sauceman

BEWARE, THIS IS A LONG READ

Some members here have shown interest as to why and how some of us can get pretty decent gas mileages with our TSX.

Since the gas prices have risen to disproportions, it becomes the right time to worry about saving up on gas. For folks like me, it is because of the high mileages we travel, we are on a budget for gas, and need to watch the way we consume gas. Another reason would be, like I stated in another thread, to keep as independent as possible for the oil companies who openly and blatantly abuse from their position of control over us since gas is a necessity for the vast majority of North Americans. And others, still a little like me love statistics, and will try and get the best mileages out of their cars just for the kicks of it..

For every member here who is interested in improving their gas mileage, here is certainly where I can help the most, since driving is a major part of my worktime, and I pay for, and use, my own car for work. Since 1994, I have accumulated over 560,000 miles of experience with my Hondas.

So I will try my best and share all the little tricks I know of, to help make your car as fuel efficient as its potential will allow it. Some things are obvious, some others are very minor details, almost ridiculous, but they have a role to play nevertheless.

Most of us already know this, but we, as Honda owners are lucky to benefit from cars built by a manufacturer whose priority is fuel efficiency and emmissions control. These two go together hand in hand. And Honda is a leader for this type of car, so, as a result, we get cars that have great potential, so far as fuel economy is concerned. The TSX fits into this category very well. Name me a 200hp gas car that can achieve 35+ mpg. You will not find too many.

That being said, the popular belief says that if you want a truely economical car, go the diesel route. That belief is false, though I will not expand on this, but if you take into account the added costs of buying a car with a diesel engine, maintenance and repair costs, the little added fuel economy you will actually gain over a well driven Civic (not talking hybrid here), will be completely overweighed by those added costs. When VW says that you can achieve 775miles with a single tank of diesel on their TDI's, they are right, but what they don't say, is that you have to drive at a constant whopping 44mph to attain this number, which is plainly unrealistic, and usually also dangerous.

So this post will address fuel economy on gas powered cars, in general, but most basic principles will also apply to diesel engines as well.

To well understand what needs to be done to achieve full economy potential on our cars, we need to know what factors can hinder fuel economy. There are 3 major areas to watch out for:

Driving Methods, namely, in accordance with our driving environment.
Physical / Environmental Factors (outside the car)
Mechanical Factors

1. Driving Methods

When we look at car stats, usually there are two levels of fuel economy shown, one for highway, and the other for city driving.

For both types of driving, it is important to keep the following basic principles in mind:

A) To achieve good fuel consumption, it is important to drive smoothly , so you must avoid accelerating hard and braking hard. Also, you must avoid overrevving the engine.
B) Curbs are to be taken as wide angled as safely possible, in order to lose the least speed as possible. This will require knowing how to use your apexes. And again, common sense says that when it's not safe to do it, don't do it.
C) Make good use of the car's energy by making the most of its inertia. Instead of relying so heavily on the brakes, anticipate a slow traffic area, and coast down to a slower speed in neutral. In the case of approaching a traffic jam, this may actually be a safe method of driving for others around you, because you will not surprise them since you don't slam the brakes on at the last moment. And I know some will say coasting down is not good for the transmition, but I have never experienced any troubles of any kind with my transmitions, so I believe there are no damages to be related to coasting down in neutral. On the opposite, downshifting causes wear to all the drivetrain.
If you arrive at a stop sign from 55 mph, you can drop it into neutral from as far as a mile away, and coast down without being too much of a disturbance for the traffic, and this is especially true with the TSX, being such an aerodynamic car that it is, it just rolls on forever in neutral.
But you need again to use your common sense; if doing this is dangerous in a certain area, well for God's sake, don't do it. If you need to decelerate quicker than in neutral, downshifting will be good too, because then the throttle and the injectors close, so no fuel is spent usually during rpms over 1500.
As much as safely possible, use your steering instead of your brakes. Try losing the least possible inertia when something comes up, either by steering your way around it when it can be safely done, or by coasting down. Braking is wasting inertia. It means you could probably have let go of the gas earlier.
D) Weight is your enemy. Keep your car as empty as possible. Don't carry more than you need to carry.
E) When you have the choice, choose to drive on highways that are made of concrete, rather than asphalt. Concrete is less abrasive, and you will see an average of 10% increase in your fuel economy.

Highway Driving

- Obviously, on highways, fuel economy=reduced speed. On most cars, the optimal speed for fuel economy ranges between 50 and 60 mph. I have found that the TSX seems the most fuel efficient at 55mph.
- It is always slightly better to drive at that speed without using the cruise control, because you can modulate and adapt to changing environments like hills, which will require from you to anticipate and increase your speed before climbing uphill so that you don't need to WOT (Wide Open Throttle) and / or downshift at the middle of the climb because the car is slowing down too much.
- As said, anticipate what is coming before you, and make good use of your car's inertia, it will make you travel for free, since hardly any gas is used when idling your way down a hill. At 55mph, you can switch to neutral on a 4-5° slope with the TSX and maintain your speed. At 65mph, it works with 6°+ slopes. On a long trip, it can save you a few dozens of miles worth of gas. I estimated that on my drive of 683 miles on a single gas tank, over 30 miles of road I had rolled on in neutral (saved a gallon there).
- Another trick, (although truckers don't like this), is following them at a safe distance, in the areas of 125-150 ft behind, and try and take advantage of their draft. This can save you as much as 30% of gas, but I doubt any trucker will let you stick to his ass for more than 15 minutes without trying to get rid of you, lol. Same goes for cars. Following cars is always better than leading as far as air draft is concerned, especially on windy days.

City Driving

It is possible to make great gains in the city.

- Accelerate as smoothly as possible. Usually, I try not to rev past 2500rpm. With quick shifts, and the TSX 6MT's short gearing, I remain in the traffic.
- Slow down as smoothly as possible, anticipate, and coast in neutral as much as you can. It is realistic to cover more distance in the city in neutral than in gear!
- When turning, try to avoid going back to 1st gear, 2nd will keep the car smooth, but devour gas less. Wider angled corners like left hand turns, may well allow you to stay in 3rd gear, which is even better. Actaully, always use taller gears when you can.
- In stop and go traffic, you can make things a lot better by keeping your distances, and acting as a shock absorber would. When the car in front of you accelerates, anticipate and start accelerating before him (without hitting him!!), smoothly, and let him floor it if he wants. Let the distance build, then as soon as he starts slowing down again, coast back to him in neutral. This will save you gas, clutch and brake. This way you can be more than twice as fuel efficient. It also will have a side effect of leaving you less stressed out in traffic jams when you concentrate on driving well instead of cutting others, or blocking others from cutting you off.
- Again, try steering your way around things. Braking wastes your car's inertia, and forces you to accelerate your way back up.

Mountain Roads

The same principles apply here;

- If you make good use of your car's inertia, and anticipate climbs by accelerating before you start climbing, you will not have to WOT and / or downshift halfway up, and use more gas than you should.
- Also, you can use inertia while going down a hill, as said before, and the TSX is especially good at that, thanks to its sleek underbody design, and it's diffuser. Why use gas to ride the car down a hill when it can very well roll it down by its own weight in neutral? And nothing wrong with going past 55mph in neutral, the higher the speed you reach, the longer you can cruise down in neutral back on the flats.
- After having coasted in neutral, rev-match to get back in 6th gear, that way you will not compress the engine when letting go of the clutch. It takes more gas to reaccelerate that 3 or 4 mph you just lost than a small kick on the throttle with no load on the engine.

Doing this can help you be as fuel efficient, if not more than driving on flatlands. I have experienced this time after time.

2. Physical / Environmental Factors

We get all sorts of weather all year round, and varying weather can greatly affect fuel economy for a car. Here are a few ways to make the best of different weathers.

For all weathers, heat needs to be kept under the hood as much as possible without overheating the car. Heat being mainly energy loss coming from the engine, you want to use it while you still have it.

All parts that are lubricated work better with some sort of heat. This is especially true during winter. When these parts are cold, they will start producing their own heat. Why not use the one that is radiated from the engine to keep all other accessories warm, except for the battery.

The battery needs to be as well insulated from the engine bay's heat as possible though, since it will hinder it's performance and cause the alternator to compensate, and thus adding more drag on the engine.

To keep the heat inside the hood, it is good to insulate it. (will be discussed in the cold weather section) This is especially true with most Hondas since they have engines that don't produce much heat. Keeping the engine bay hot will let parts like the exhaust and cat do their job right, the O2 sensor will be able to command a more accurate air / fuel mixture. Also, and this goes against the laws of performance, but the more the intake air is hot, the less dense it is, so the ECU will adjust the ratio and end up needing less fuel. You will slightly lose power this way, but also save up on gas.

A good insulated engine bay will also help keep the heat inside longer, hopefully reducing the amount of cold starts to a minimum, which are pretty hard on gas. This especially helps during winter months, when more engine starts are very cold starts.

Hot Weather

Aside from the above principles, if you can exempt yourself from using the A/C, you should automatically do so. But what is the better compromise? A/C or open windows?. On other threads, this issue has been adressed, and it has been said that A/C is better than open windows, because they act literally as a parachute. I agree with this, but only on the highway, at cruising speeds. In the city, under 40mph, you're better off not using the A/C, but opening the car windows instead.

Making a good use of the A/C: Try using the A/C when you're at highway speeds if you need to, or when decelerating. Avoid as much as possible using it when you are accelerating, since it robs the engine of about 15-20 ft-lb, costing that much more gas.

Another small trick that works really well, and I have mentionned it in another thread before also, if you're going to fill up your car with gas, do so in the morning before hitting the road. This is valid when temperatures rise above 40-50°f (7-10°C). Gas in the stations' reservoirs is at much lower temperature in summer than outside ambient teperature. When you fill the car up with this cooler gas, the gas will slowly heat up, and expand in volume while doing so. So when you hit the road, the gas will slowly expand and you will use gas that is solely the product of the expansion for up to 20-25 miles, depending on the temperature difference. Again, this I have experienced time after time.

But if you fill up at the end of the day, especially the way I fill it up, the gas will expand, and simply overflow in your driveway, and it will be a loss.

Rain And Snow

Try avoiding puddles of water and sludge. Try driving on drier parts of the road, or parts that are free from snow accumulation. This will reduce resistance for the tires. To illustrate how much resistance snow can offer, I was once driving in Manitoba, when I hit a blizzard between Winnipeg and Brandon. When trying to pass a truck, I came up to an area where there was forest and no wind to clear the road of the snow. All of a sudden, I found myself driving in about 10 inches of fluffy snow. I was driving at 65 mph, and trying to accelerate to make the pass, but I had the pedal to the floor, in 3rd gear, and I couldn't accelerate any more, because the snow was slowing me down too much. That was with my Accord 95 EX-R. It is extreme, but it shows that snow or water can and does offer resistance, and adds load to the engine. So the less there is the better for fuel economy.

Cold Weather

Here the cold gas trick doesn't work for you, it actually works against you when temperatures drop below 35°F. The best you can do then is fill up at the warmest part of the day. But it is a losing deal nevertheless.

This is when a good, well insulated hood is really useful, especially in the Northern US, and Canada. Hopefully, your engine bay will be well insulated enough that you won't do a complete cold start after ½ an hour after you last stopped the engine (Edit, After one complete winter, the TSX tends to stay colder during idle, and does lose heat pretty quickly despite its heat shield). To help improve this, you may want to restrict the area of your radiator that is exposed to airflow, in order to keep the engine warmer, and longer. And I'm talking in case the temperatures drops well below 20°F (-10°C).

Now I know this may be a shocker for some of you, but freezing your ass for 5 minutes because you don't preheat the car saves you a lot of gas. It's better to use your heated seats instead. You can start your engines and drive right away even when it goes down to -40°F/C. It will not damage or wear anything prematurely, and there again, I can back it up with my own experience. I have never used a blockheater, and very seldom pre-heated the car (except by consideration for my wife who's always chilled to the bone), and again I have never noticed any premature wear on the engine. In fact, I have lasted all of my engines for over 220,000 miles, except for the one I hydrolocked, but that's another story. If you still don't believe me, tell me then what is the difference with heating up the car, while it cold idles at around 2000-2500 rpm, or driving it away, smoothly at the same rpms? It would hurt the transmition? False. When you heat up the engine, the transmition oil does not heat up, so there is no difference, except you will double the gas consumption, because the transmition will heat up while driving anyways.

Windy Weather

There is no magic formula if you must drive against the wind, except for trying to make the most of any vehicle's draft, but especially from trucks. If you can stick behind trucks and draft them, it will help you save a significant amount of gas.

3. Mechanical Factors

This is the part where we can waste a lot of gas unconsciously, because so many parts of the car are involved in good fuel efficiency. There is a fair amount of maintenance that can be done, but also some modifications can be made to enhance good fuel economy.

Maintenace Of Mechanical Parts

Make sure:
- Tire pressure is up to factory specs (eg: Michelin recommends 32 PSI cold).
- Must have the OEM tire size (less than spec may also help, but to the detriment of handling).
- alignment must be optimal, and OEM.
- OEM front end (no aftermarket lips, as longer lips will increase the Cd)
- Use the right recommended octane rating (91 for the TSX).
- Make sure the fuel filter is not clogged.
- Make sure the air filter is not clogged.
- Make sure the O2 sensor is clean.
- Make sure the throttle body is clean.
- Make sure the catalyst is clean.
- Make sure you don't have exhaust leaks.
- Use OEM sparkplugs, service them at factory recommended intervals.
- Use OEM plug wires as well as distributors.
- Make sure all grounds are clean.
- Make sure all battery poles are clean.
- When the battery loses efficiency, replace it. If you don't, the alternator will start working overtime, get overloaded, and create more drag.
- Make sure powersteering and brake fluids are full.
- Change oil at factory-recommended intervals.
- Use 5W30 or 5W20 when allowed by Honda. This oil was designed to help improve gas mileage. But unfortuantely, 5W20 is not for the TSX.

There are other factors for sure, but they don't come to my mind just now. But feel free to add if you know of any other.

Modifications To Enhance Fuel Economy

- Weight is your enemy. Strip as much as you dare to, things that are not of any use for you, as if you were to strip it for a drag night. Just don't touch any parts that would negatively affect it's aerodynamism.
- Lightweight flywheel and clutch assembly.
- Underdrive pulley set.
- Insulated exhaust header and downpipe all the way to the catalyst.
- Higher compression internals will improve thermodynamic efficiency, but it will not be worth the cost, unless you have something else in mind, like the occasionnal night at the tracks.
- A flat aluminum undercarriage will help improve a lot on the Cd, but you will need to take into consideration the cooling of the engine, how you will evacuate the hot air gulped in by the radiator. Note that the TSX is probably the most well developed sedan when it comes to undercarriage aerodynamics, so you need not worry about this.

As a conclusion, I'm sure other tricks can be added, and if you know of some, it would be nice if you added them. Also, it would be wonderful if this article helped you make fuel economy gains, and it would be great if you posted the results here.

Many of the tricks, as I stated above will help very minorly, and/or apply only in certain situations, but adding them up is where you will get good results.

Also keep in mind that there is no such thing as ideal conditions on the highway, so you will never know for sure the true potential of your car, but that should keep you freaks trying more for better results. If you can, and do try all of these tricks, I think you are a little nuts, but more power to you, and you will be able to achieve incredible numbers, as much as 10 mpg over the EPA ratings for your car.

Y2K4 TSX

Now *that's* an informative and well-written post. SUPER job.

rb4580

Thanks for the write up

sauceman

Thanks guys.
I wanted to wish you good luck and good evening, but I actually had to edit because the post was slightly too long. Maximum allowed characters is 20,000. So now we all know, lol.

Count Blah

Wow. Why didn't you just buy a Hybrid?

dom

You have my vote for post of the month, great job.

One thing though, how do I insulate my engine compartment?

LurchRSX

Good post.......damn you take your fuel economy seriously.....my eyes hurt frrom reading

larchmont

Wow. A textbook! Nice job. Even though I admit I didn't read every word

.....but, as they say, it's nice to know it's there!


One quibble -- or, I guess, a question. Regarding how appx. 50-55 mph is usually the most fuel-efficient speed: I always assumed this, but, from what I've seen on the Trip Computer (which I've come to accept as extremely reliable), this doesn't seem to be clearly so, at least on the TSX, and at least with my car which happens to be the 5AT. Granted, the naked-eye seat-of-your-pants technique isn't extremely accurate, but I do observe pretty well when I try -- and I tried pretty hard on this. And, I swear, from what I could tell, the efficiency at 70 was not perceptibly worse than at 50. Not in the least.

Whaddya think, sauce???

Brad

Thanks for the write up!!

One item puzzles me. Strip it for a drag night? I've never done anything like that (never wanted to), but isn't stripping and going drag sort of the opposite of each other? I would imagine that going naked as much as one would dare is the opposite of someone who cross-dresses (as in drag) in an extremely overstated manner, no?

XPLORx4

Wow, nice, informative post. You certainly take fuel economy seriously!

When you drove that 683-mile tank of gas, what car was that in? If it was the TSX, and you drove all 17.1 gallons worth (not likely), that's nearly 40 mpg!! If you used only 16 (which is pretty darn near the limit), that's 42mpg!

What conditions were present? Weather, road surface, altitude, road grade, average mph?

Let's consider that 683-mile trip as an example. At 55mph (avg), it would take about 12-1/2 hours, assuming no food/drink/potty breaks. If you used 17 gallons of gas consumption at $2.399, that's a cost of $40.78. Since I don't actually know your average speed for that tank of gas, I don't know how long that trip would have actually taken.

Now, repeat the exercise, except let's go 75 mph (avg). At 75 (avg speed), without observing any fuel economy tips (blatantly violating them frequently), I was able to get about 28.6 mpg from 16 gallons of gas (over 458 miles), taking roughly 6 hours. This occurred last weekend on a trip from Gilbert, AZ to Mojave, CA, where I refueled. Using the figures I obtained, let's extrapolate the cost over 683 miles and see how much better I might have done driving with fuel economy as my main objective (again, assuming 55 mph instead of 75).

683 mi / 28.6 mpg @ 75mph = 23.88g
23.88g x $2.399 = $57.28
683 mi / 75mph = ~9 hrs + 10 min refuel time

Driving 75 gets me to my destination about 3-1/4 hours earlier, but costs me just $16.50 extra. So, I suppose if my time is worth less than $5/hr it would be worth it for me to drive with a keen sense for fuel efficiency, but personally, I'd rather arrive 3 hours earlier.

No offense intended; I'm not criticizing your methodology at all, just pointing out that it's not always beneficial to maximize fuel economy in all situations. But 683 miles to a tank of gas is darn impressive, no matter what kind of car it is.

Just my 2 cents.

XPLORx4

Hahah. Funny play on words. I guess "drag strip" is an oxymoron, eh?

darth62

I work at home 2 days a week now. Beat that strategy for saving fuel!

shabaaz

You were driving 65 mph through 10 inches of snow??? Are you nuts, you could have killed yourself. I am a Winnipegger(or should i say winterpegger) and know what its like during our winters. I almost lost it driving throught 6 inches of snow only going like 40 mph. The car becomes like a sled, the bottom of the car just slides on the snow and tires loose contact with the road. I guess the snow was heavier that time.

Anyway, thats some good advise. thanks

Brad

Oh wait! Drag Racing Strip! Oh... I had the impression of someone removing their clothes to save weight, that was, to strip if you dare...and drag.

At the San Mateo Country Historical Museum in beautiful downtown Redwood City is a display of horseless buggies and carriages, most of which were 100 or so years old. One of the buggy's model name was called something like Drag Trap. I guess back then there was nothing quite like a hawlin' dragster...in the nude? It was a small buggy--light-weight too.

I had better stop before my foot gets any deeper in my mouth.

larchmont

Let's just hope floozy doesn't see this post.

zircon

The strategies sound solid generally, but I also have a quibble. I would never tail a truck to get better mileage. My biggest fear when driving is trucks thowing stones and nuking your paint and glass. To me, the enhanced gas mil. is not worth that idea. Also diesel exhaust is toxic.

majormojo

I hear ya. My time's worth a little more than $5/hr too. But it certainly was a detailed and informative post.

I just filled the tank on the TSX tonight, 47 L for 542 km. That's about 28mpg, same as you and 520km of that was on the highway @120 - 140 km/hr. Seems pretty darn reasonable to me. In the case of that 520km drive, the time spent driving is definitely more important than saving a couple bucks.

Regarding 683 mi to a tank, that's kind of relative. For steady highway driving at 120 km/hr (75mph) I can do the same (1100-1200 km) on a tank of gas in my Suburban. However, that tank is something a little over 155 litres, so filling it up definitely lightens the wallet.

sauceman

Well, I do take fuel economy seriously, but I never push it as far as I wrote up in this article. Driving sensations matters a lot to me, this is why I have the TSX. I do have fun with the car from time to time, like yesterday with the 911 GT3. But usually, during worktime, I try to be reasonnably easy on the gas.

sauceman

Thanks domn, Lurch and Larchmont.

Larch you are probably right about this, and it is probably because of the 5AT's gearing. They statistically are supposed to be more fuel efficient than the 6MT, so you may very well be still good at 70.

But take a look to compare if it still is the case when the engine comes under load, like when you climb a hill, or drive against the wind, to see if it remains as economical as driving at 55. I'd love to know this, I'm sort of wondering.

larchmont

What I can tell you right away -- and probably this is no news to you, but it was news to me -- I can tell you that either of those factors just DESTROYS the fuel efficiency. I would have thought they'd be slight but significant factors. Actually they are EXTREME factors. Like, instead of 35-40 mpg (which is a typical routine cruising rate on the freeway), you get 10-15 (or maybe less or more, depending of course on the amount of upgrade or wind).

So, I'm not too interested if it's a little better or a little worse at different speeds. I know it matters, but it's hard to get interested in whether it's 13 mpg rather than 10 mpg if I drive 55 instead of 75. Both of the mpg numbers are so crappy -- and so aberrant -- that I don't even want to think about it. It's like, that doesn't count. Even though I know it does.


P.S. Heck, maybe I'll check anyway. You got me curious.

sauceman

Yes, you do have a point.

It is up to you all to see up to what point you can go in your efforts to drive economically. While driving at 55/65 on the freeway is optimum for me, it may not be for everyone. You can still apply most fuel saving principles driving at 80. Only not the speed one, lol!

Anyways, my job lets me take it easy on the road, but I know of many others who have to literally race between their rendez-vous, and could never afford driving easily. It's always a question of being reasonnable, if it's good for you, do it, but if not, then don't, it doesn't matter that much.

One little thing I'd like to add, and maybe it'll help you see my background and where I come from. Some of you probably read about my hatred for gas companies' way of dealing abusively with their customers, and how I try to be the least dependent of them as possible. There is something else.

I was no choir child on the road. I used to accumulate speeding tickets, because frankly, I adore speed. If I copuld drive at 140mph on the roads, I'd do it day in, day out. And I finally lost my drivers' license because of to many tickets. So I learned my lesson, slowed down, and found out 3 benefits: 1. I no longer needed to have a budget for speeding tickets (!), 2. I was saving up big time on fuel, and 3. I found a way of solving my road rage problem. Once I had put myself to mind that I was driving around at 60, no matter what other speed other people drove at, that it didn't matter if I wasn't the fastest around, then I started to become the gentleman that I am on the road, plus, when I arrived home, I wasn't nearly as exhausted as I used to be.

So I adopted this way of driving-- but only on weekdays, generally, weekends I save for fun, without going overboard, though.

EDIT: 683 miles was with 19 gallons, good for 36mpg.

sauceman

Yeah, I know, that was foolish. It wasn't as bad as it looked, though, even from the inside of the car, when, occasionally, the snow was high enough to start going over the hood, but the snow was soo fluffy, and it didn't pull either to the left or the right. I felt pretty comfortable, but still, it was kinda dumb, I know.

Those were other days, I guess. BTW, that trip yielded me the most extreme driving conditions I ever encountered. I remember arriving back in Thunder Bay from Saskatoon after driving for 16 hours, and the last 8 hours in a snow storm so bad I couldn't see more than 10 ft in front of me at times. My eyes were bloodshot.

Anyways, good times.

larchmont

Verrrry interesting. And makes a lot of sense.

Aggressive driving probably isn't worth it, on any rational level. But then again, maybe most of what we do doesn't make sense on any rational level. Beavis and Butt-head had it right when they said, "People are stupid."

We make our choices. Most of the time we decide well enough. And we're happy to settle for that. Even when the fact is that we could do better.

sauceman

ROFL!

Actually, what I meant was stripping the car of some accessories like the spare tire, jack, etc. Just like you'd strip it from the car when going to drag race on friday nights, or whenever it is in your local area.

lol, I'd love to see that... OH NO!!! Mental picture! mental picture!... except maybe...OOooh! girls......... hehehe

sauceman

dom

Sauce, how do you insulate the engine bay to keep it warmer ??

LurchRSX

Which car was the 1074km done in??

STL

I am fairly certain the TSX comes with a 4-wire O2 sensor. Two of those wires are for a heater element inside the sensor that is able to quickly get the sensor to operating temperature. So I don't think keeping the engine bay hot will help the O2 sensor work any better.

sauceman

domn, one thing you can do for the TSX would be to cover up partially your radiator, but really, I think that as far as the TSX is concerned, the job has really been well done already. Originally, this thread was written by me on Honda-Tech.com, and was concerning all Hondas, many of which could have been improved.

Lurch, I travelled 1094km with the TSX in July on a single tank of 72 litres.

MSB128

Great info...thanks for taking the time to write that up.

XPLORx4

sauceman- how did you fit 72l/19g of gas into a 64l/17.1g fuel tank?

dabuda

nice info, didnt know there was a science to getting good mpg

majormojo

sauceman, thanks for the info. You've obviously put some real thought into this. I do have a question/quibble though and that's wrt to (over)filling the tank with "cold" fuel. I'm not certain what you're trying to accomplish by doing this? I can't see how this can change fuel economy in any positive way, all it could do is extend the driving range of a single tank of fuel. Is that your goal?

As you probably know, in Canada, gasoline is sold volume-corrected to 15 deg. C. There are temp sensors in the pumps that adjust the actual pumped volume based on the temp of the fuel. No matter what the temp of the fuel when it's pumped, you're always buying the same amount (mass) of fuel per litre displayed on the pump meter. So if the fuel happens to be colder than 15C, the volume of fuel that ends up in the tank is going to be slightly less than what the pump meter says.

Keep in mind that this effect is very very small. The thermal coefficient of volumetric expansion for gasoline is about 9.50x10-4/deg C. Given say, 50L of fuel and a 20 degree difference, we're talking about less than one litre change in volume. But still NO CHANGE in the actual amount (mass) of fuel in the tank. If the fuel warms up in the tank and expands, you're not getting any more fuel - there's no more energy potential in it than when it was cold. It's just taking up more space.

I'm not sure that overfilling is such a great idea in the first place. It could be dangerous if you're in an accident with the tank and filler neck all overfilled with fuel. In addition, one could argue that the fuel economy would be worse because of the extra weight. 25L of fuel weighs about 50 lbs... I bet one could get consistently better fuel economy by only ever filling the tank halfway. Beats removing the rear seat cushions to save weight.

Anyway, lots of good info there, sauce. thx

Brad

The Ebony interior would be most suitable for nude driving, BTW.

However, having learned that everything except the perforated part of the seat is plastic-vinyl-something, the appeal has diminished.

fdl

Well this post is certainly a sharp contrast to my "whos getting the worst gas miliage" thread. Very interesting stuff ....although dont forget to have SOME fun with the car too!

sauceman

We discussed this a few weeks ago in this thread:
Overfill Gas Tank thread

fdl

Between that post and this one..you are definately the undisputed king of fuel mileage!

sauceman

Majormojo, thanks for the very pertinent post.

The goal of the cold fuel trick is effectively to cheat and extend the mileage you do with a single tank by playing with the thermal expansion of the gas.

I knew about the gas being corrected at 15°C in Canada, and I would too be curious to know what it is in the US. Thanks, though for bringing up the formula for calculating thermal expansions for liquid gasoline, I searched for it, but did not find it. I must admit that I expected the diatation to be more important than it really is. I see myself corrected for this.

True there isn't more energy potential in the gas tank, but as the gas expands, the outside air also does have expanded, and both combine to form a larger volume, not as dense though, but it doesn't really matter, because there is only a specific volume that will enter each cylinder of the engine on each cycle. So, for each cycle, the fact that there is slightly less density entering the cylinders, there ends up being more gas left in the tank after identical amounts of engine cycles when the temperature is higher.

Also a little note about overfilling the gas tank. It would, i agree be the ideal if we could constantly drive with the gas tank only partly filled up, due to the weight situation, but it is not practical. Also, having 10 more litres (75 instead of 65) would be a very minimal difference in weight, and in fact, the difference in fuel consumption could arguably be offset by the fact that you need to stop less frequently for fueling up, and thus waste less gas in the process doing so. But I would qualify this calculation as going overboard with the whole question, lol.

But you must be aware that in case of a car crash, a gas tank full to the neck represents a lot less risk than a tank with nearly only vapours in it. To ignite, it needs oxygen. When it is full, you don't have any (unless there is a spill, but then that is uncontrollable), but when it is empty, with only gas vapours and air left in the tank, boy are you sitting on a bomb!

Thanks for your post, and the extra information you provided.

sauceman

Lol, well, I think not too many girls (Re: Slapshot) would appreciate my light weight apparel in my ebony interior'd TSX, 'cept maybe my wife.

sauceman

Heheh...

You know what, I am sure that it might help some others do the same mileages with their cars if some are willing to try it, and even maybe beat my score, especially in the case of a 5AT. Actually, I would be very curious to know what that car is capable of.