How to get better gas mileage

dear tom and ray, several times i have called in your show but have never received a call back. i would like to share with the car talk community of something i know for a fact you would be interested in a way to get better gas mileage, no boggus devices that doesn’t work. from what i could discern from my experiment using non-ethanol gasoline gives me in my kia soul a 50% improved gas mileage, i don’t know what it would give everybody else, but i know it made a huge difference in my car. please reply back or call me, i would be honored in talking with you guys, i have started a new religion and it’s cartalkians. i listen to your show religiously lol

Tom and Ray don’t respond in these forums, and I doubt they read them.

Are you comparing non-ethanol gas to E-85 (85% ethanol, 15% gasoline)? If so, I believe your claim. If you are comparing non-ethanol gas to E-10 (10% ethanol, 90% gasoline), I think you need to reexamine your measuring methods. Pure gasoline will outperform E-10 in terms of fuel economy, but not by such a wide margin.

By the way, this is not new knowledge. This topic has been beaten to death in this forum. Many people already know that adding ethanol to gasoline will lower fuel economy. Ethanol also pollutes more. The fact that it’s in your fuel is a sign of the corn lobby’s power.

As Whitey said. I’d just add that going from E10 to ethanol free I’d expect maybe a 10% gain. 50% is way out there…

The basic story is that ethanol has less energy by volume.

Since ethanol contains oxygen it’s partly ‘pre-burned’ in a sense.

An interesting post. Improvements in fuel economy can be made by eliminating ethanol. Whitey is right in everything he said, incuding the comment about the lobbyists for the ethanol producers’ 54-producer consortium.

If you look at it from a purely gas mileage perspective, your ethanol-elimination works. But if you look at it from the prospective of reducing use of foreign oil, it does not. At least, that’s the “official” version. In truth, when the fuel necessary to grow and harvest the necessary crops is factored in, ethanol may not even reduce the use of foreign oil.

I thought one of the Reasons for E10 was to help improve emissions.

It certainly changes the chemical make-up of the emissions, and I believe that was the original intent, but I think, recently, we’ve discovered it just substitutes one kind of pollution for another, and the new kind is actually slightly worse than those produced by gasoline. Will someone who knows the specifics please fill in the gaps? I don’t remember where I read it, or I would refer to the source and give you more details. I’ll do a search later and see if I can find some specifics.

I think you got it right, Whitey, I read a couple of years ago a study (Stanford?) that looked at all the pollutants from the emissions, and concluded that E10 was about the same as regular gas overall, so the ‘cut the pollution’ benefits that E10 was originally sold on aren’t really there.

As for the original question, if the OP’s taking about going from E85 to pure gas, then the 50% might be about right, since it’s about a 30% drop going the other way. But I didn"t think a Kia Soul was a ‘flex fuel’ vehicle.

I searched this forum for “ethanol pollution” and what I found is that ethanol replaced MTBE (methyl tertiary butyl ether) as an octane booster. MTBE is a really bad pollutant, so replacing it with ethanol did reduce pollution. As to whether E-10 pollutes less than pure gasoline, that question is currently unanswered.

MTBE was replaced here in NH because of ground water pollution. Once it gets in the groundwater it’s very difficult to get out. Ethanol seems to breakdown very quickly and doesn’t pose as much of a problem.

well, all i can say is the numbers don’t lie. i haven’t changed my driving style and this week i actually worsened my driving style. and still before when i was using 10% ethanol 90% gasoline 87 octane, and went with 90 octane no ethanol my milage per tank went from 130-150 miles on a tank to 230-270 miles per tank, i calculated 50% because on a travel that normally takes me 1/4 of a gas tank back and forth now takes me 1/8 of a tank exactly. so maybe you don’t agree with this but all i can say is my dad had me take down my mileage per fill up and so far it’s consistent i haven’t gotten below 230 miles on a tank. has a matter of fact, this week i had 1/8 of a gas tank left and i had reach 235 miles on the tank when i filled up. i could’ve kept going for a while easy.

i can post an attachment of the receipts if you would like

You’re not being very precise in your calculation of mileage. You can’t go by your fuel level gauge. You have to divide your total miles traveled by gallons used. 1/8 or tank, 1/4 tank, etc is very imprecise.

Reality: you may improve mpg by about 5% - 8% by using non-ethanol. No more, that’s just a fact.

Sorry…but ONE tank full isn’t a valid calculation. For any accurate measurement you’ll need 30+ tank fulls and then take the average.


No wonder your calculations are so far off. You can’t go just by tank-fulls, unless you empty the tank each time. That’s just too imprecise of a method. Here is what you should do:

  1. Next time you fill up the tank, reset the trip odometer or note the odometer reading. Fill the tank all the way to the first click (don’t top off).

  2. Next time you gas-up, use the same pump at the same time of day. Fill the tank all the way to the first click (don’t top off). Determine how many gallons of fuel it took to fill the tank (in gallons), and how many miles you drove. Write these numbers down.

  3. Divide the miles you drove by the gallons used, and you will get a more precise estimate of your fuel economy. Since the miles driven will only be to the nearest 10th of a mile, round your result to the nearest whole number. Still use the #.### gallons figure to the third decimal place, but your result can’t be more precise than the least precise number used to calculate your MPG figure.

For example, on my motorcycle’s last tank of gas, I rode about 106.4 miles, and used about 2.371 gallons of fuel, so I know I got about 45 MPG.

Your fuel gauge, even if it’s digital, isn’t accurate enough to calculate fuel economy accurately. In fact, your odometer isn’t that accurate either, but it will at least give you an objective measurement to start with.

Mike is correct that this will only give you a rough estimate. If you want to be more precise, you need to repeat this process and average the results over time.

I’ve tried pure gas against E-10 and have seen very little difference over several tanks, but I have noticed in my daily driver that I do get better mileage using certain brands over others. I normally get about 10% better mileage when using gas purchased at Walmart or Texaco than if I use Citgo and I’ve tested this multiple times over the past several years. There are many things to factor in when it comes to fuel mileage. Cars get better gas mileage in the summer than they do in the winter, because winter blend gas isn’t as good and engines and drive trains are not as efficient in the winter because of the cold weather. Driving habits and traffic conditions are not going to be persistent from one tank to the next. Even on a car I’ve been driving for 18 years and have personally put over 370K miles on my fuel mileage normally varies by 0-3 mpg from one tank to the other. Others are correct about the way to figure gas mileage and you can probably get a pretty good mileage average over 5-10 tanks of the same fuel. Often people will also drive differently (not saying you do) when they do something such as change from one fuel to another or add a so called fuel saving device which will skew the true results. I suggest using the same fuel during the same time of year (winter, summer) for 10 tanks to see what mileage you get then switch to the other fuel for 10 tanks to get a true average using both fuels. I also have to agree than you probably are not getting that much better mileage, but if you are congratulations and stick with it.

“I have noticed in my daily driver that I do get better mileage using certain brands over others”

I went down this road before. See where it got me:

I’m glad I stayed out of that one.

In addition to revising your testing procedure, may I also suggest to brush up on captialization and paragraphs. If you don’t use those tools correctly, it kind of makes you look like a rube - and it’s hard to take a rube seriously.