bzyrice

iTrader: (10)

So, when I drive my car I try to get above 26 mpg. 26 is the most I have ever gotten so far. It makes me sad though when I see others hitting 30 mpg on a regular basis. My usual mpg is 24. This is with mixed driving in city and highway.

So, my question is, what is the most efficient rpm to drive at? I find myself shifting all the way to 6th even when I am going only 30 mph to try and get more mpg. lol Is this the right way to get more mpg? I also tried shifting anytime the car gets to 3000. Should I shift sooner?

Thanks!

georgegiorgio

Tire pressure set at least 35 PSI

Use Premium Unleaded Fuel

Don't hit the gas too fast, aka don't step on the gas pedal too heavily

Since it's manual, change gears between 2,000 to 3,000 RPM, better doing so around 2,000 to 2,500 RPM, the higher you go, the more gas you waste

Don't break too strong

Never possible, put your car in neutral, like gliding downhill, or while waiting the traffic lights, cuz, the engine's RPM would lowered, that'll help to save some gas...

Don't stuff your car with too many heavy stuff...

Don't drive with the windows open...

On the freeway, keep between 65 MPH to 80 MPH, better at 75 MPH, my experience anything under 75 MPH and above 80 MPH, translate poor MPG.

Lastly, use synthetic motor oil, and good oil filter..

SouthernBoy

Don't go into 6th at 30 MPH. This could potential hurt your engine.

Just drive normal, and by that I mean easily. Not to the point where you're a hindrance to other drivers, but use forethought, plan your moves, and apply some good common sense.

The best I have ever managed in a week of work commuting was when my car still had the OEM tires one it (EL42's). It was in the summer and I got 27.98 for a week's driving back and forth to work. My commute is not normally in heavy stop and go traffic, but it is through residential areas and the business sections of a town. Speeds go from 25-30 to around 50 on my drive. For that week, I was really trying to get the best mileage I could.

Best on the highway was also with those tires. It was in the summer of '05 on a vacation trip with the A/C running the entire time and two people on board. Speeds between 62 and 78 MPH netted 33.94 MPG for the first leg of the trip.

Just take it easy and drive "normally". Don't push it and don't stress the engine. Tires do have quite an effect on mileage. At present, I am averaging a little over 24 for my in and around town driving with work commute with Michelin Pilot Sport A/S Plus tires pressured to factory spec. Highway is slightly over 32 with these tires.

01tl4tl

read your owner book for minimum shift speeds and rpms for each gear
read any of the dozen threads here on saving fuel

6spdtl-s

iTrader: (1)

I think optimum speed is around 55-60mph or so. Anything past that and wind resistance starts to pick up pretty hard.

Integral212

I think it's hard on the engine to lug it, so make sure not to end up below 2K while accelerating.

Also, I believe our cars have a fuel cut-off, so if you are downshifting and engine braking, there is no fuel consumption (with the car in gear). The injector duty cycle is zero. If you shift to neutral instead, the car must consume a tiny bit of fuel keeping the engine idling. Engine braking therefore can save both brake wear and fuel if you do it right - w/ rev matching.

It's also safer to decelerate in gear since you have power available if you need it, for crash avoidance.

bzyrice

iTrader: (10)

Ive read alot of the fuel saving threads.. I think my question is more for what gears should I drive in .. I didnt know that being in 6 gear going 30 would hurt the engine? How does it hurt the engine?

PhilB81

Lol no 30 mph in 6th u got to be near full throttle to keep rolling. The user manual has recommended shift points. I don't have access to it now but I can post them tomorrow if needed.

Also +1 on the keeping the car in gear vs idling as your rolling to a stop. When in gear and off the throttle no fuel goes in if you pull it out it has to idle so fuel goes in

Integral212

Lots of ways to describe it. Think about the charge of gas and air in the cylinder. It blows up and generates a certain amount of energy. This normally moves the piston a certain distance (the power stroke). If the piston is at such a tremendous mechanical disadvantage, the charge explodes but the piston can't move much. This makes the effective pressure for that stroke much higher, and stresses the rods and bearings. Try idling uphill in first gear. It works fine. If you try and idle up hill in second gear, the engine starts vibrating and the revs drop way down. That's basically what you're doing when you shift too early. I've heard people repeatedly say "but I've driven my car that way for years." That's fine. There's margin for error. But why stress your engine that way? Btw - this is not an issue with the transmission or the drivertrain. It's the engine that gets the abuse. Also, if the engine is lugging at low speed and vibrating, it's probably not doing any favors for the engine mounts either (though, you could say the same thing for hard acceleration).

SouthernBoy

Just a minor correction. The fuel/air mixture does not explode in a reciprocating piston engine. It burns. Were it to explode, you would lose your engine very quickly.

SouthernBoy

Think gear ratios, load conditions, and RPMs. If you understand all of these concepts, you will also understand that driving in 6th gear at 30 MPH (which would equate to around 1500 RPM), is really going to stress your engine. Try not to go into 6th gear below 50 MPH and even at that speed it should be good, level road. The TL engine just does not produce that much torque.

bzyrice

iTrader: (10)

Yah I want to see what the manual suggests as shift points.. can someone post that up?

PhilB81

Okay here are the shifts as per my 08 manual.

1st to 2nd at 17 mph (27 kmh)
2nd to 3rd at 27 mph (43 kmh)
3rd to 4th at 36 mph (58 kmh)
4th to 5th at 41 mph (66 kmh)
5th to 6th at 44 mph (71 kmh)

I personally hold my gear a bit longer especially 5th.

bzyrice

iTrader: (10)

what is your gas mileage? Since you follow this?

rockstar143

iTrader: (6)

Hmmm...I'll have to try this RJ...
I average about 21mpg for the most part and I do about 60% highway. I'd probably be happy at 24 or 26. I think a LOT has to do with the really hot climate we live in. Most of the dudes getting close to 30 are up North. Imagine how our cars would drive if they drove how they drive in the winter, year round.

PhilB81

I'm mostly around town on roads with stoplights and speed limits of 45 to 55 mph. I average 21 mpg, and I do get on it every once in a while. When I drive more highway let's say 70-80% highway I get 28 mpg.

As far as cold weather driving, your economy will get worse in the winter because the air is denser. So although you have more power (more oxygen in the combustion chamber which then the ecu puts more fuel) you have to constantly fight against thicker air, so highway cruising is harder on fuel economy.

bzyrice

iTrader: (10)

yah like i said the best I have gotten is 26 mpg .. that was all highway.. going 75 miles an hour in 6th gear.. i still dont get how they get 30+mpg! maybe its my 19" wheels? I dunno.. i wil test this out soon since I just picked me up a set of 18" aspecs which are lighter..

94eg!

I regularly average 31/32mpg w/ mostly freeway when I drive my 6MT. I did once manage a 31mpg two way average in city traffic. There is some good info in this thread and some bad. Here's my personal tips...

A light foot is the number one thing. Accelerate slowly and smoothly and use the owner's manual recommended shift points. A little higher rpm shifts going uphill, and a little lower rpm shifts going downhill is also the way to go. Try to maintain a constant speed, and keep an eye on stop lights ahead so you can let off the gas way early and coast to them.

Don't coast with the car in neutral. This wastes fuel because its being used to idle the engine. When you leave the car in gear and let off the gas, the injectors get shut off completely. The vehicle's momentum is being used to keep the vehicle's electrical system running and that's more effecient. Of course you will slow a little quicker, but usually you are coasting down-hill or to a stop light anyways. BTW: The injectors stay off until the engine hits around 1200rpm. at which time it trys to idle the motor by force to keep it from stalling...

On the freeway, follow behind other cars. When your out in front, you are the one pushing all the air out of the way, and this hurts your mileage. Drafting really helps at freeway speeds. Don't get too close cause it's very dangerous to tail-gate. You'de be surprised at how far the draft actually reaches behind an SUV or Minivan. Just beware of dirty trucks, gravel haulers or stones in the road. Nobody likes paint chips.

Don't use the AC when driving at slow speeds. Roll the windows down and enjoy the fresh air. The compressor uses engine power which requires more gasoline.

At freeway speeds, keep the windows up and use the AC when it's hot. This increases aerodynamics and makes up for the small amount of power being used by the compressor. Also using the auto temp control will reduce AC usage. Set the temp a little higher when you want better mileage (if you can stand it). Also switching the compressor off manualy for hills and passing helps conserve fuel as well (the more rpm, the more loss from the compressor).

Maintain a lower speed on the freeway. If you drop your typical speed by 5mph, you will see a significant difference in mpg's. Wind resistance is the killer of mileage. Because of the air, it takes 4 times as much power to go twice as fast...

rockstar143

iTrader: (6)

Hmmm...I could swear I normally get better gas mileage during winter months. Then again, winter for us is low 70's down here in South Florida, which is probably the happy medium.

princelybug

iTrader: (16)

Nice. So, just out of curiosity, what is the maximum speed we can go in each gear in our 6MT Type-S's?

Anybody?

blkaspec

when your are comparing mpg figures, are you only looking at MTs? because the AT is more fuel efficient based on the gearing, but it does this at a loss in performance. i can drive around 80mph and get around 28mpg, and if i lower that to 70mph i get 31-32mpg as long as i dont push it. i average 26-28 with about 80% highway, but i do push it hard and drive on the quicker side.

94eg!

I had a 08 TL Auto loaner and I could not get near as good mileage driving in the same manor (2mpg lower). AT transmissions have hydraulic pumps that sap extra power from the drivetrain at all times. It's like driving around with the AC compressor running at all times. Simply less effecient than manual...

And as for gearing, I'm not so sure it makes that much of difference. I have a Civic with a Type-R motor swap that cruises 75mph at 4000rpm. It still gets 36mpg. The original motor was .3L smaller and cruised 75mph at 2800rpm and only got 35mpg... lol

long gearing sucks!

PhilB81

well, firstly, if you have larger wheels, you're actually traveling further than your mileage indicator shows. So your MPG will show a lower amount than what it actually is. [even doing the math yourself with fuel and miles traveled will be wrong, unless you know that from point a to point b was exactly lets say 100miles verified via gps or something]
Also, wider tires/wheels decrease your fuel economy.

Oh, I didn't realize you're in the sunshine state. Than, that's different, in the summer your A/C is getting a beating, the compressor runs in cycles, but i'm sure that in the summer it stays in the 'on' cycle much longer. I checked it on the highway, and at 75mph, compressor on vs off drops the econ about 3-4mpg.
Also, at some higher ambiant temperatures, my guess is that the car works pretty hard to keep itself cool and engine loses some efficiency, so even in a less dense medium [air] the car needs more effort to move itself.

blkaspec

i understand your logic, and you are probably correct, but i have read many a threads that have discussed this and they all came up with the AT getting better mpg. most attribute it to the gearing and the RPMs at normal speeds. i am just relaying info more than claiming something. and if you are calculating mpg via the car's computer, i would say a 2-3 mpg error is not abnormal. either way i think the keys to getting better mpg are all listed and other than that there is not much else one can do.

bzyrice

iTrader: (10)

So, with this thread I have figured out one thing I do that sucks up gas .. When i see a stop sign or red light I will automatically go into neutral. I thought this saved gas. guess I was wrong.. so no more coasting for me going to the lights.. I just hate the sound manuals make when you are not putting gas into the gear..

So basically I should do this.. If I am exiting the freeway and I see a red light at the end of the exit ramp:
1. Keep the car in the gear I am in.
2. Let go of the gas.
3. Do not put into neutral until I hit 1300 RPMs..
(Should I down shift til I am in first gear and 1300 rpms?) I hate slowing my car down using the tranny..

Does this sound right? I am going to try this this next week to see what I can get..

Rockstar.. how do you drive your car? When do you shift?

94eg!

I wouldn't bother with downshifting. It might save you some brake pads, but it's gonna put extra wear on the clutch (which would you rather replace?). Even if your a heel-toe rev-matching hero, there's really no point. The only time I do this is if I'm going down hill, and I only go down a couple gears (not all 6). Just slow down in current gear till you feel the car start to kick (~1000rpm) and then put the clutch in. No biggie...

PhilB81

ya, i wouldn't downshift to 1st no way!! on a long ramp, or coasting from lets say 60mph to a stop light, most i do, is from 6th, i blip the throttle, put in 4th, and coast from there. then when i'm at around 800rpm, i just push it out of 4th, don't need the clutch.

There's been plenty of debate about if you need to always push in the clutch no matter what, and from what I gathered if there's no load and everything is matched really well, there's no harm to not using the clutch, and u save the spring a tad bit.

94eg!

I forgot to mention that you really shouldn't be afraid of rpm. The shift points in the owners manual are for regular acceleration. If you are going up hill, more rpm is better than more throttle to get you going.

In top gear on the freeway, I feel it's better to downshift to 5th for bigger hills, rather than add a bunch of throttle. A higher throttle position adds considerably more fuel (richens the mixture). If you add too much throttle, you can easily surpass the amount of fuel being consumed by the next lower gear.

This is because of thermal efficiency. Motors are more efficient at different rpms with different loads. Sometimes it's difficult to pick the right one. Trial & error and personal judgment comes into play here...

SouthernBoy

You're half right. Our cars do get lower fuel economy in the colder months but not because of "thicker" air. It's because there is more oxygen in a cubic foot of the stuff. This causes the ECU to increase the fuel shot via the injectors to try to maintain the optimum ratio which is between 14.7:1 and 15:1. This results in more power and less mileage. In the summer months, the opposite is true.

Integral212

Regarding your earlier comment about burning vs. exploding, it was a good observation. One thing I would add to the above is that in colder climates (like MN where I am), they also oxygenate the gas with ethanol in the winter months which creates a drop in mileage. I don't think it's mandatory for premium, so I think it varies whether or not you're getting ethanol with the 91 or 92 octane up here. It definitely creates a mileage hit in addition to the different stoich balance for cold air.

94eg!

I think you guys are all off base as far as the air density and all that. Mileage is worse during the summer becuase a hot gallon of fuel is less dense than a cold one. This means when you fill up in the summer, your actually putting less fuel in the tank. As a result, the same size tank of gas doesn't drive you as far. They even adjust the price of gasoline accordingly in the summer months. It would be nice if we could pay by weight rather than volume...

As far as the air density and power are concerned, that is true. But it only becomes an issue at wide open throttle. In part throttle situations, your foot will only allow as much in as need to go the desired speed. In hot months, that means more throttle to go the same speed. The difference is gradual and very small, so it mostly goes un-noticed...

Aman

Coasting in gear is important. It'll take a bit to get used to it, but once you do, you'll save quite a few mpgs here and there.

1. Coast when coming to a stop (obviously) If you see a light red way ahead of you, off the gas right then and there. coast as long as possible, chances are the light will turn green before you come up to it (depending on how far it was when you started coasting0 and you won't even need to brake.
Coast when coming up to a stop sign with a line of cars. If there are 3-4 cars at a stop, don't come up and get in line. What I do is coast, let the car slow itself down, and by then all the cars ahead of you should be through the stop, and you save some gas there.
Coast on any downhill, no matter how steep. Car will maintain speed.

2. Accelerate slowly and smoothly. Pretend you're driving your grandmother around. Or you're chauffering Joan Rivers. Whatever works. Just drive smoothly, and no jerky accelerating.

3. Don't go past 2500. I've got a 4-cylinder auto Accord, and I can get it to shift as early as 2200 rpm. You could try that, but 2500 is a good starting point.

4. Cruise in the highest possible gear. Now this doesn't mean 6th at 30mph, but once you get up to speed on a normal city street, 4th is good, even 5th in some stretches, depending on your gear ratios.

5. Try increasing tire pressure when you get your Aspecs mounted. 5 psi above recommended should be fine for what you'll be doing. People will be talking about how it's unsafe to go that high above recommended psi, but look on your tire sidewall, most have a max psi of about 50-60 psi. As long as you don't drive like a maniac, you're safe. People have even gone 10psi above recommended, but at that point it might not be good for your tires in the long run.

6. Get rid of any useless weight. This includes anything you may have in your trunk. I've got a bunch of completely usless stuff, from cleaning supplies, to a spare gas can, to some lawn chairs, to an umbrella. Get rid of it all. Except the spare tire, don't risk that.

7. Weigh your Aspecs and your 19s. They'll probably be different by about 8-10 pounds (ish) per wheel. It is said that 1 pound of unsprung weight is equal to 10 pounds of sprung weight. So you could save the equivalent of up to 400 pounds! You probably won't, but you'll feel the difference for sure.

8. Don't bother turning off your engine if it'll be idling for less than about a minute. It actually takes up more gas turning your engine off and on than just leaving it on for about that time. It's different for different cars, and I think the Accord/TL uses a starting system that's more fuel-efficient than most, but still.

That's my
well, a bit more than just two, but you get the idea

Aman

At most fuel stations, gas is volume corrected to 15 C, so that's not a big problem.

PhilB81

I agree with what you say, but the bottom line is the air the car has to break in order to travel. Colder air is denser, the ecu senses that and compensates with more fuel, therefore you get more power. So, if the car didn't have to split air to travel, in cold climate you would need to press slightly less on the throttle to maintain a constant speed of let's say 70mph, however that won't happen because in cold climates the air is denser and you need extra work to propell the car.

Let's pretend the car is traveling in a caccumed tube and you have a hose supplying it air to the engine. If the air supplied to the engine is warm, the ecu puts in less fuel to match the combustion ratio, result is you have to push a bit more on the throttle to keep a certain speed. However, if now you provide cold air to the engine you no longer need to push as hard on the throttle to maintain that speed, but bottom one same amount of fuel went into the engine. I'm sure you know that the throttle pedal controls airflow and the ecu controls fuel flow.
Again different example (vaccume tube again, disregarding air drag), let's pretend you need 50hp to maintain 70mph and in hot weather that means your throttle pedal is pushed down 30%. if it's cold you still need those 50hp but this time since air is denser you only need to push the throttle 20%. And in both scenarios same amount of fuel goes into the engine. If with cold air you push your pedal down 30% you'll just endup going 80mph let's say.
So really what comes into play is the medium the car travels through when it comes to fuel ecnomy. And in really high temps, well the car is probably running wide open through the radiator and longer ac compressor cycles = more work for the engine, therefore more fuel consumption.

Aman

but colder air has more oxygen, which equals a bigger combustion in the chamber, which equals less fuel needed. This is how CAIs work, except they increase power instead of efficiency.

YeuEmMaiMai

I averaged 28mpg when I drove an 08 TL auto for a week while they were putting the trans in my 02 CLS that was with a mix of 30% city and 70% highway.

In my CL-S driving the same route I get about 27.

i let the car shift around 2100 rpm for 1-2 and 2-3 and then the car shifts at lower points as the speed builds. the new PCM won't shift up to 5th until 45 versus 40 for the old one.

YeuEmMaiMai

it also take more effort to move a cold car
it also takes a while longer for a cold car to reach operating temp

When I go on my road trip to MI in november, I notice no difference in fuel economy versus my spring road trip in May to MI. I get 31mpg

PhilB81

Oxygen isn't a fuel, more oxygen you have, the more power you have but that includes burning more fuel. If simply putting more air in the combustion chamber = more power without needing more fuel all cars with forced induction would get phenomenal fuel economy.
CAIs work with improving the flow of air and sucking in more denser/cooler air. This results in more power, not less fuel consumption.

SouthernBoy

Actually fuel economy increases during the warmer months for the reasons I already gave.

Basically gentlemen, here's what happens. Your car has a number of sensors which report to the ECU which in turn, evaluates conditions and makes the necessary adjustments to deliver the best 1) fuel economy, 2) emissions reduction, 3) the most power; all under the condition in which the car is operating coupled with the driver's demands.

In the warmer months, there is less oxygen per cubic foot of air drawn into the engine to mix with raw fuel. The OX sensor will read this as a potentially rich mixture and will lean out the fuel shot in order to correct this condition and attempt to reach the desired ratio. This results in less power produced (which is why your engine does not feel as torquey in those months as it does in the colder months). As long as you are driving normal, the engine will make sufficient power (torque) to motivate the car. You should see an increase in fuel economy during the summer over that of the winter if conditions and driving are similar.

In the colder months, the reverse of all of this takes place. More oxygen per cubic foot of air means a potentially lean condition, so the ECU increases the fuel shot to rectify the situation. More power, potentially more emissions (that's why special additives are added to fuel during these months), and lower fuel economy.

I hope this helps.

SouthernBoy

This is true and it does cost in terms of economy.