ejh7977

I have an 03 TL and have been very frustrated with the gas mileage I have been getting. The best mileage I have gotten was about 370+ to the tank and that was when I used mid-grade (89) gas. I switched to premium a few months ago and got pretty decent mileage around 350 - 360. But things have just been getting bad the last 5 or 6 tanks of gas.. around 300 - 310 (using premium (93)). So I am very stumped as to what could be causing the terrible mileage. For shits and giggles I tried using regular to see what would happen and I saw my mileage jump to around 335 to 340 on 87 octane. I am pretty sure it has something to do with the fuel since the change occurs the moment I leave the pump (I drive it until the gas light comes on) so I see the difference right away. I am just wondering if my knock sensor is giving false readings to the computer. When I use regular gas I seem to get the better mileage now but I still don't detect any knocking so the sensor seems to still be working at least for regular grade gas. Has anyone encountered anything like this in their TL before? The only other thing different now is that I replaced the normal stock air filter element with a K&N brand. I have heard that these filters allow more airflow to the engine but I still am not sure this is a factor but just wanted to add that info here.

Any help would be greatly appreciated.

fsttyms1

Well for 1 that mileage in the TL is good mileage Period. most will hate you cause they dont get any where near that. 2 is your location and daily/weekly driving, subtle variations can cause that said drop or increase. Also look for fuel that doesnt have ethenol in it. To me you have nothing wrong with your car

samkws

in cold weather the gas mileage decreases a lot

and i think u r getting a gd mileage

anything below 18 is not normal, but seems like u r avg 20-22 at least

ejh7977

wow, you think getting 290 to 300 miles to the tank is great for a TL? I guess i never knew what the average TL gets for mileage. I noticed my mileage drop while driving the same conditions daily (same route with the same traffic conditions). Climate control is set to Auto so it's not like I force it on or off all the time also having the same relative outdoor temp.

I have also had mileage that seemed opposite of my driving habits at times... sometimes when I'd be getting really good mileage i would be in non-stop city traffic and doing hard accelerating as well. And then other times i'd have the worst mileage (around 290) while cruising at 65mph on all highway. Nothing seems to have any rhyme or reason with this car LOL. But I guess I'll put on a happy face for apparently getting great mileage with my car.

Thanks for the info, Eric

sbuswell

winter=less than optimal gas mileage period. rest of the year= much better. usually the hotter it is the better gas mileage you will get. i think it has something to do with the fact that fuel expand with heat so when it is dispursed by your feul injectors it is already warm or very warm and expand more than cold fuel will. I would bet that if there were gas tank heaters that would regulate your gas temp(maybe there is already) then you would not see much if any difference at all in colder temps. the other factor the bare in mind is the different gas you are actually putting intom your car in the winter. I know it is different but can't remember why. some of the science majors on here may be able to shed some light on this subject. BTW 300+ a tank of a TL in the winter is good!

03CoupeV6

I ran my current tank dry today (been doing lots of driving lately).

It would not restart at 467.6 miles. This was 87 octane, I rarely use premium. In my car, I see no gas mileage or performance benefit from premium (believe me I've tested it).

I know, I know from Kris on this.

03CoupeV6

I should add that the gas light came on at around 395 miles for that tank, and the rest was driving with it on. I purposely wanted to see how far it would go.

In my 100% city driving I get the gas light around 330 miles consistently. So, to the original poster, there is nothing wrong with your TL.

MikePA

Do yourself a favor and actually compute mpg instead of the meaningless miles per tank.

sbuswell

better yet miles until gas light comes on because that is all that really matters. if gas light comes on get some gas. better than having the sediment from the bottom of your tank dirtying your fuel filter.

fsttyms1

200k of running past the low fuel light no issues here

SK2003TypeS

I normally get 18-20 mpg with 80/20 city/hwy, which is fine with me.

My previous 2 tanks, I avg'd 11 and 12 mpg. The difference (from what I know) was that I had done a lot more city driving than normal (~95%). Maybe did 1 or 2 short hwy drives about 10 miles. I'd think the mileage would go down with the city driving, but not that significant. Still a little baffled by this.

The current tank (I'm almost at half) I'm back on par heading towards 18-20 mpg. With this tank, I'm back to a 80/20 city/hwy split. Before filling with this tank, I dumped some Chev Techron in and used a different Exxon station (both have 10% ethenol). I only use 93.

03CoupeV6

The fuel is pumped from the bottom of the tank even when the tank is full, so this has no merit - sorry.

Phesto

that reminds me of my 65 mustangv8 i was prolly getting like 8-10mpg ALWAYS

loud_whispers

Here is an article from our Service News section on Gas Mileage:


Squeezing the Most Pennies From Your Fuel Economy Dollar

Oil prices are climbing, and that can only mean
some painful price hikes at the fuel pump. These
days, fuel economy is a serious concern for many
drivers. But squeezing the most pennies from
one’s fuel economy dollar is no easy task. It takes
some skillful driving and a vehicle that’s properly
maintained.
Here are some helpful tips to keep in mind and to
share with your customers:

• Set Correct Tire Pressures - Use an accurate
tire gauge to set the tire pressures to the
recommended values listed on the driver’s
doorjamb sticker. These values are the
recommended cold inflation pressures that are
the best compromise for ride quality, steering
feel, handling, and fuel economy. When
replacing tires, always go with OEM tires;
they’re optimized for low rolling resistance.

• Use the Correct Engine Oil - A higher
viscosity engine oil increases internal engine
drag, and that reduces fuel mileage. Always
use the recommended engine oil for your
vehicle.

• Accelerate Moderately and Smoothly -
Avoid pressing the accelerator pedal
excessively. Hard acceleration burns a lot of
fuel. Very slow acceleration keeps the
transmission in its lower gears too long, which
also increases fuel consumption. Moderate
acceleration gives the best fuel economy. If the
vehicle has M/T, you can boost your fuel
economy by upshifting as early as possible. If
the vehicle has Sequential SportShift, leave the
shift lever in D.

• Avoid Stop-and-Go Driving - Anticipate
traffic signals to keep the vehicle’s momentum
going. Avoid unnecessary stops and starts.
Don’t tailgate; hugging the bumper in front of
you forces you to make the same stops and
starts as the vehicle that bumper’s bolted to.
Use the cruise control as much as possible to
keep your speed consistent.

• Minimize Braking - Every time you brake
while driving, you have to accelerate again,
and that uses fuel. When decelerating, take
your foot off of the accelerator pedal or use
light braking.

• Use A/C Sparingly - The engine works
harder when the A/C is running, and that
reduces your fuel mileage. Turn on the A/C
only when you really need it. If the vehicle has
climate control, select the warmest
temperature that’s still comfortable.

• Reduce Speed - Aerodynamic drag has a big
effect on fuel mileage at speeds above
45 mph. Reduce your speed and you reduce
the drag. Trailers, car top carriers, roof racks,
and bike racks are also big contributors to
increased drag.

• Reduce Vehicle Weight - Unnecessary items
in the vehicle add weight. That makes the
engine work harder and use more fuel.
Remove the stuff you don’t need from the
passenger compartment, trunk, or cargo area.

• Use a Block Heater in Cold Weather - As
the air temperature drops, more fuel is wasted
heating up the engine to its normal operating
temperature after a cold start, and the engine
oil is thicker, increasing internal engine drag.
Also, at temperatures below 40° to 50°F, fuel
doesn’t vaporize properly, so more of it must
be used to get the engine to run properly
during warm-up. A block heater helps keep
both the engine and the engine oil warm and
reduces the extra fuel needed at colder
temperatures.

• Avoid Short Trips If Possible - The engine
uses a lot of fuel to warm up to its normal
operating temperature (about 180°F), and it
has to deal with higher internal friction before
it does. The shorter the trip, the more fuel
that’s wasted warming up the engine and is
lost to higher internal engine friction. For short
trips, try walking or bicycling if you can. If you
need to drive, keep in mind your fuel
economy will drop quite a bit. This is
especially true if you’re making those short
trips on a cold day, or you’re making them on
a hot day and you’re running the A/C to
quickly cool down the vehicle. Such
conditions can easily reduce your fuel
economy by more than 25 percent.

loud_whispers

Winter and Summer Fuels

To better match fuel properties with differences in seasonal temperature, oil companies change their fuel formulas twice a year: winter and summer. They make these changes the same time each year for a given area, and most customers never notice it unless it gets
unseasonably hot or cold. So what’s the difference between winter and summer fuel?

• Winter fuel vaporizes at a lower temperature than summer fuel. This is good for cool
weather, but if the air temp gets above 90°F (80°F at higher altitudes), winter fuel can
cause hot-start difficulties, poor initial idle, and initial stumbling.

• Summer fuel vaporizes at a higher temperature than winter fuel. This makes it
suitable for warm weather, but if it’s used at low temps, summer fuel can cause long crank
times and stalling. If you’re hearing lots of driveability complaints from customers and your winter weather is unusually hot, suggest they switch to a high-volume, name-brand fuel (to reduce the possibility of poor quality), and hope that the weather returns to normal. To fix starting problems in the meantime, tell customers to crank the engine for 5 seconds without pressing the accelerator. Then if the engine still doesn’t start, press the accelerator halfway down, and continue cranking until it does start. For more info on engine starting, see the owner’s manual.



Have fun reading. Just some random postings i dug up from ISIS.

Marlboro27s

300 to the gas light is very good mileage. when the gas light goes on it takes around 14 gallons, which is around 22 mpg

i usually get 290 because i drive city. during highway driving ive gotten around 370 to the tank. the gas mileage in the TL is VERY different between city and highway. ive gotten as low as 16mpg city, and as high as 30mpg during road trips

slewis78

I just drove 3300 miles for a vacation. I alway use Premium, always. I averaged 28mpg (some city, mostly highway). But what I do is clear the tripometer, drive, then refill the tank entirely (still it auto-shutoffs). MPG is then the number of gallons used to refill the tank (till the pump shuts off) divided by the numbr of miles on the tripometer (and to double check, the fuel gauge should be a little beyond the full-tank mark). That's just how I do it, and I rarely drive till the fuel light comes on. Remember not all gas is the same, so different gas stations will have different quality gas. On a road trip, you can never predict which gas stations will be available (and even same brand gas stations might not all get the same gas). But locally, I always get gas at SAMS since it's on the way to work.

With such a high compression ratio, I thought the TL required Premium? I have a 2000 TL -- same engine as in 2003's, right? Interesting to hear some of you guys are getting away with 87 and 89. I thought in general VTEC engines required Premium. Still, I always get over 300 miles to tank (currently I'm at around 70,000 miles on the car).

I'll stick with Premium always, but good to know that in a pinch, the TL engine could use 89 if I had to...

03CoupeV6

I'm not buying into the TL requiring premium for any other reason than the Acura badge. Simply put, my 2005 V6 Accord (J30A4) has a 3.0L V6 pumping 240hp with a compression ratio of 10:1 and it requires regular fuel only. Yes, there is a gain from premium, but the requirement is 87.

The TL's 3.2L V6 (J32A1) has only a 9.8:1 compression ratio and requires premium. It's obviously not compression ratios, or the Accord would also require premium.

A couple of tanks ago, I ran my TL from completely full to completely empty where it would no longer start. It went 467.6 miles on one tank of 87 octane. I have totally stopped using premium. My TL not only seems to get some of the highest gas mileage on this board, but it has very good performance as well - and doesn't react any differently to regular than premium. If your's does, then use premium - but you won't hurt it by using regular.

fsttyms1

I gaurentee if you dyno the car with the 2 different you will see a HP difference. Motor trend did it awhile ago with the Oddyese van and it was almos 1 sec slower in the 1/4 mile.

03CoupeV6

But doesn't the Odyssey require regular? If the TL performs any differently, I can't tell it - and the gas mileage isn't any different (tested). I don't really get the chance to test the performance around here. Lately, I've been driving the TL like a Camry anyway, though, so I wouldn't know.

mdavisii

I consistently get the gas light at around 275-290 miles with 100% city driving. Usually fill 'er up around 320-340 miles. I believe the MPGs are slightly lower for the '99 model TLs because of the four speed tranny (19-CTY 27-HWY), but I am very satisfied with my mileage as well.

Highway I usually get about 250 miles to half tank, and about 375 miles when the light comes on.

fsttyms1

No back when they did it it required Premium (and i think they still do )

fsttyms1

I let my mother use my car today and she did the "nice" thing and filled er up. And guess what. 87. well off to drive it out of the tank!

MikePA

Now I understand, upscale model = premium fuel. Makes sense to me. It's all marketing. Glad there are folks like you to see through this advertising fog and reveal the truth to us.

03CoupeV6

I see you disregarded the comparison to the Accord's V6, which is higher-compression and higher-output requiring 87 octane.

And I'll say it again - Regular fuel in my TL doesn't result in any noticeable difference.

MikePA

No, I didn't ignore it. It's irrelevant.

fsttyms1

Thats not the truth at all!

MikePA

It's not????? Who's gonna break the news to 03COUPEv6??

03CoupeV6

What I meant was:

The TL may benefit from premium fuel (increased power), but based on my personal experience - it does NOT require it. If there is a performance difference, I cannot tell. And there is NO gas mileage difference in my TL.

ejh7977

Here is an article I came across a few months ago that convinced me that I really don't need premium:

Do You Really Need Premium?
And Answers to Other Gasoline Questions
By Edmunds.com Editors
Date Posted 07-05-2005
Buying premium gas is like taking vitamins — you can't always feel the difference and yet you know it's the right thing to do. But as gas prices climb, paying the extra dime per gallon for premium is like adding insult to injury. Eventually, the thought is bound to jump into your head: do I really need to pop for premium?

Until about 15 years ago, if a car called for premium gas and you pumped in regular, the car began to knock and ping and even vibrate. But that was before they essentially put a laptop under the hood of the automobile, said Dr. Loren Beard, senior manager of Environmental and Energy Planning, for Daimler Chrysler. Now, sensors take readings and tune the engine as you drive by adjusting the timing for whatever fuel you put in the tank.

The result is that a car that calls for the midgrade gasoline will usually run on regular without knocking, Beard said. However, its performance will suffer slightly. How much? It will be perhaps a half-second slower going from zero to 60 mph.

Volvo cars call for "premium fuel [91 octane or better] for optimum performance and fuel economy," said Wayne Baldwin, product/segment manager S60/S80. "However, there is absolutely nothing wrong with using 87 octane as the knock sensors and engine management system 'protect' the engine from knocking."

Baldwin, a former rally driver who competed in SCCA Pro Rally events said that engines have changed a lot in the past 15 years. "Cars built before 1990 probably do not have knock sensors and many brands back then relied on high-compression ratios for the best performance. Today [performance comes from] electronically controlled spark curves, turbos, variable valve timing, supercharging and knock sensors."

Issues of performance aside, Baldwin said you should never use gasoline that causes your car to knock. "Constant knocking or detonation is a real bad thing for engines," he said.

When choosing what grade of gasoline to use, Steve Mazor, principle auto engineer for Auto Club of Southern California, said it is important to read the owner's manual carefully. The key is to figure out whether premium gasoline is "required" or "recommended." If it is recommended then a driver could opt to use a lower grade of gas, if they were willing to accept slightly reduced performance and fuel economy.

However, Mazor added, "We don't recommend that people switch down. Let's say you switch down to regular, and you have to accelerate to avoid an accident and it doesn't accelerate fast enough. The Auto Club can't be responsible for causing that situation."

Edmunds.com has a Volvo S40 in its fleet, so we consulted the owner's manual to see the exact phrasing in regard to fuel requirements. It said, "Volvo engines are designed for optimum performance on unleaded premium gasoline with an AKI (Anti Knock Index) of 91 or above. The minimum octane requirement is AKI 87." It appears that Volvo is making a recommendation for premium gas but is not requiring it.

In Edmunds.com's Forums debates abound over the pros and cons of using different fuel grades. One member even suggested there was only one type of gasoline, no difference — except for price — between regular and premium. Other members recommended using premium gas even if the manual called for regular. We put this question to Mazor and Beard.

Mazor: "All this does is do a very good job of draining your wallet. People used to put in a tank of premium to get 'the good stuff' to help their engines stay clean. But now they put detergents in all grades so it doesn't really get you anything."

Beard: "If you have car designed to run on 87 [octane], it doesn't help to run it on higher-octane-level gas. But there are several exceptions." He said that the 3.5-liter Chrysler engines are designed to run on midgrade gas (89 octane) and it allows them to advertise a certain peak horsepower. However, it will run well on regular gas. "The difference is very small," he said.

Interestingly, Mazor noted that at some gas stations, there are only two grades of gas. However, they blend the regular and premium at the pump to produce the midgrade gasoline. This allows them to have only two underground tanks for the gas storage.

In Edmunds' forums some drivers expressed concern about the quality of gas sold at independent gas stations and advised sticking to the so-called "name" brands of gasoline.

"Typically the only difference is the additive package they put in the gas," Beard said. The additive package is often put into the gas as the tanker is filled up at the refinery. A common additive is a detergent agent. "The law requires a certain level of detergents in gasoline. Shell for example is putting in more detergent — whether that has a measurable effect to the driver is debatable."

Detergents have a marked effect on engine deposits. "If you take apart a modern engine that has been running on a modern fuel, and compare this to an old engine that was running on old gas, you can see an obvious difference," Mazor said.

The biggest difference between today's gas and the gas sold 15 years ago is the removal of lead. Taking out the lead, and developing effective catalytic converters to more completely burn emissions, have radically cut pollution.

While oil companies like to advertise the magical powers of their gasoline, it appears that there is very little difference between brands. Most drivers fill up at the nearest gas station or the one for which they carry a credit card.

Does a gas expert like Beard have a preference when buying gas? "I just watch the light on the dash. After it has been on for a day I get nervous and go to the closest station available."

ejh7977

And here is another article clipping:

The main advantage of premium-grade gas is that it allows automakers to advertise a few more horsepower by designing and tuning engines to take advantage of premium's anti-knock properties. But auto engineers generally agree that if you use regular in a premium engine, the power loss is so slight, most drivers can't tell.

"I go back and forth, and I'm hard-pressed to notice" whether there's regular or premium in the tank, says Jeff Jetter, principal chemist at Honda Research and Development Americas. He drives an Acura designed for premium.

Import brands, especially, use premium fuel to distinguish their upmarket models. Most Toyotas, for instance, are designed to run on regular or midgrade, while the automaker's Lexus luxury brand prefers premium. Same with Honda and its Acura luxury line.

"Generally, the more expensive the vehicle, the higher the expectation for performance and the more the customer is willing to pay for fuel," says Pete Haidos, head of product planning for Nissan in the USA.

All Porsche engines are designed for premium, too, but it's not available everywhere. "Our cars must be able to drive all over the world, and so we are able to run on regular," says Jakob Neusser, director of powertrain development at Porsche's research and development center in Weissach, Germany. "You don't have to feel that a mechanical problem or anything else will happen" using regular gas, even in the highest-performance, regular-production Porsches.

Premium, in fact, sometimes is worse fuel than regular. It resists knock because it's harder to ignite than lower-octane fuels. As a result, some engines won't start as quickly or run as smoothly on premium, notes Gibbs, the SAE fuel expert.

High-test does have a potential fuel economy benefit. It is slightly denser than lower-octane gas, meaning there's a little more energy in a gallon. But the small difference is hard to measure in real-world use, and that same density can contribute to undesirable buildup of waste products inside the engine.

No data show that engines designed strictly for regular run better or longer on premium.

The Federal Trade Commission, in a consumer notice, emphasizes: "(I)n most cases, using a higher-octane gasoline than your owner's manual recommends offers absolutely no benefit. It won't make your car perform better, go faster, get better mileage or run cleaner."

There is "no way of taking advantage of premium in a regular-grade car," says Furey.

"There is no gain. You're wasting money," insists Jim Blenkarn, in charge of powertrains at Nissan in the USA.

"No customer should ever be deluded into thinking there's any value in buying a higher grade of octane than we specify," says Toyota's Paul Williamsen, technical expert and trainer.

But premium retains a mystique.

Even Mayne, the sensible Subaru owner who has switched to regular, says she'll buy premium when her neighborhood station has a special price. "It's my perception that I might get better gas mileage or that it might be better for my engine," she says.

"I would stop driving rather than use a lower grade of gasoline," says Andrew Martschenko of Boston, who drives a 2003 Nissan Maxima. Nissan says premium is "recommended" for that engine — automaker code for regular is OK, but you'll only get the advertised power on premium.

If the price difference between regular and premium grew to $1, Martschenko says, "Then I might consider trading down" to regular.

Guilt plays a part

Some people feel almost guilty, as if they are abusing their cars, when they don't burn premium, says gasoline retailer Jay Ricker, president of Ricker Oil of Anderson, Ind., which operates 28 stations. "They go all the way down to 87 (octane), but maybe every fourth tank they put in the good stuff."

Sam Turner has seen the appeal, too. He's president of Favorite Markets of Dalton, Ga., which operates 139 outlets in three states.

He recalls visiting one of his stations during a price war with a nearby station, which had cut the price of premium to just 4 cents more than regular, instead of the usual 20-cent difference.

"A customer was waiting and asked me if I was going to match the guy across the street. I said, 'Yeah,' and he said, 'Good. For 4 cents, I'm gonna buy super.' "

Contributing: Barbara Hansen

MikePA

These articles prove nothing, except it's possible to post copyrighted material.

They restate the same things that have been said in this thread, and every other thread about this topic. It's almost as common as 'How do I reset the the Maint Req' light.

Yes, the TLs computer will adjust to lower octane at the expense of performance and fuel economy. I imagine it adjusts by retarding the timing. When you do that, performance goes down as does economy.

What's the point of saving 5% on fuel and getting 6% worse fuel ecomomy, not to mention poorer performance? People on AZ install all kinds of equipment to improve performance, from CAIs to headers. What's the point of doing this then using regular?

slewis78

Uh, did you read the entire articles?

The point was that you save 5% and you don't get any worse fuel economy or engine longevity (as all modern fuel, regular and otherwise, now have detergents unlike 15+ years ago, and modern ECUs can near-instantly compenstate for differences in fuel quality). Where did you read in that 6% worse fuel economy figure? The only negative is that (potentially) you no longer get the advertised horsepower out of the engine. Most people don't care about HP, far more care about saving money.

Back when I had my turbo B18B, sure, I ran 105 octane when I pushed 18psi. And yeah, I use Premium all the time in my TL. But looks like I don't have to.

fsttyms1

Because Many of us (including my self) have seen decreases in Mileage. On 93 almost no matter how i drive i get 200 to the half tank. Lthe last couple times i tried 87 i was lucky to get 150-170 to the half. Thats more of a decrease than i i would save paying for the 93. I have also seen a slight performance degrade. The car isnt near as responsive.

03CoupeV6

My 251 miles and still above half-tank on this tank of 93 is impressive - although mileage by the fuel gauge itself is highly inaccurate. We'll see how many miles this tank goes, and how many gallons it fills up and I'll let you know the MPG.

ejh7977

Here is a current update with my erratic gas mileage situation... I am now seeing a pattern where if I put in Premium (91 or higher) I see better mileage (24-25 mpg) for the FIRST tank of premium I use. Every tank of premium I use thereafter gets me less mileage (20 - 21 mpg). Then I would get fed up with the low gas mileage and switch over to regular gas and get the same mileage (20-21 mpg). But after just one tank of regular (87) and going back over to premium (91+) I get that better mileage again (24-25 mpg) BUT ONLY FOR THAT FIRST TANK. So apparently something is happening with my car where it takes a drastic change in octane for it to utilize premium gas. Not sure if it is a computer/anti-knock sensor glitch.

And to restate the conditions: Same gas station was used every time. Same daily route during the same time of day.

Another note to add is that when my car was newer ( less than 2 years old ) I would frequently but not every time get mileage around 25 - 26 using mainly mid-grade (89). In the past year I have rarely achieved that kind of mileage even on premium... and now I only see my best mileage (24-25) on only the first tank of premium I use as subsequent premium fillups give me gas mileage equivalent to using regular 87.

So, something has degraded in my car over the years and need to have this looked at by a mechanic. Initially telling an acura mechanic of the bad mileage it was brought to my attention that it could be brake callipers that are not fully releasing but then that wouldn't make sense when I see a drastic improvement in mileage just from going from regular to premium. My best guess is that there is a glitch in some sensor or the computer.

optomos

Where do you gas up?

Bob_F

There are so many variables that go into MPG calculations that it's very hard to connect any one change to a change in MPG.

For example, how are you determining when your tank is full? If you use the gas pump's auto stop feature, be aware that they can stop at different levels. If you don't always fill to the same fuel level you will get distorted MPG results for both the tank you just completed and the tank you are about to use. For a 350 mile case, 0.5 gallon difference in filling can result in a nearly 2.0 MPG difference in calculated MPG between tanks.

Bob

ejh7977

Not sure how you can get "distorted" MPG. True that you aren't sure at what level "auto" shutoff really takes effect but i'm sure it isn't off by gallons of gas. For discrepancies at the pump to have been a factor in my 21 mpg vs. 25 mpg would have to be a difference of over 2 gallons of gas which i'm sure doesn't happen with auto shutoff. Granted i'm sure there is a slight variation of total gas in the tank after each fillup but i'm sure it isn't much more than a .1 or .2 gallons of deviation.


But even that deviation should be minimized since i'm making my calculations from using the same pump at the same station every fillup.

To answer the previous question I've been filling up at a Shell station and switching from their premium (93) and regular (87).

Bob_F

I didn't mean to suggest that fill level differences could explain the entire MPG deltas that you're recording. It was only meant to be an example of one of the many things that can effect calculated fuel economy.

For many years I used to always top off my tank beyond the auto-shutoff. I found that the amount of additional fuel that I could add varied significantly.

That's great that you're using the same pump at the same station every time. That probably eliminates that concern entirely.

In any case, I find all these octane discussions very interesting. I look forward to your future reports.

Bob