Non-alcohol gasoline = better FE.
 

If you can find it, get it. Unofficially it can get you roughly 10% better fuel economy. Subject to GREAT argument, of course.

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Man I wish I knew if this was true.

I recently had my personal best tank but I made a ton more changes so I'm not to sure if it was the non-ethanol fuel or my other changes that gave me a 4.49mpg increase.

Using higher density fuel doesn't really constitute better "FE" (or a "mod"), you are not changing the number of btus used, just the volume. Not a fan of ethanol, just saying.

there are multiple older threads about this...

where do you get 10% difference in fuel economy? if the fuel is 10% alcohol you dont lose 10%, the alcohol still contributes. i believe 10% alcohol fuel has about 3% less BTU, but the idea that it correlates directly to mileage has been debated. some even claim better mileage with 10% alcohol.

10% difference = real world results. Not just my results. I'm pretty sure I mentioned nothing about linearity between the percent of alcohol and fuel mileage gain. Sorry if my first post implied this.

Any time you add methanol or ethanol, you are reducing BTUs even comparing same octane fuels.

I support that 10%....
 

When I use 10% mix gas i get about 10% less mileage...sounds kinda weird but true...just try it.

When road tripping last month I actually got my best mileage running E10. We made no effort to conserve gas and still averaged around 27 the entire trip. With the E10 tanks it was 29 and 28.

*did not read thread*

You should not lose 10% economy with E10. Somewhere around 5% is normal though.

I too notice a 10% drop in fuel economy using ethanol fuel. I believe it's something with the 3800 engine and programming, as other folks with the same engine/transmission combination notice a similar drop in economy when running E10.

Now a more modern car designed/programmed for ethanol in the gas might do better on E10 than my couch.

My dad has an Impala with the 3800. I'll have to get him to run 100% gas in it.

I typically take a 5% hit on my FE with ethanol. I suspect the 10% hit that some are taking is the result of ethanol's affinity for water. E-10 will actually pull moisture from the air, up to 0.5%.

That could be. My car has an 18-gallon tank, and frequently runs for a week or two at a time with 10 or fewer gallons in the tank. So I can see how E10 drawing water into itself when it has a lot of surface area is doable.

But that begs the question of how the water gets in there in the first place. Possibly through leaky gaskets or when the evap canister draws in fresh air?

...from the EPA website:

GASOLINE lower heating value: 116,090 BTU/gal
ETHANOL lower heating value: 76,330 BTU/gal

...thus, ethanol has only 2/3's the ENERGY content of typical gasoline, although it does have a much higher OCTANE (anti-knock) value:

GASOLINE: RON = 88-98, MON = 80-88.
ETHANOL: RON = 116, MON = 112

...unfortunately, OCTANE is only useful to high-compression engines and supercharging, while ENERGY content is indicative of power and fuel economy. That's why E85 has a higher OCTANE value of 105, but actually results in 2-10% loss in power and fuel economy. If the engine had variable compression ratio (CR), most of the power loss could be reclaimed using E85 (which can use higher CR), but not the fuel economy.

...so, "yes," non-alcohol gasoline will yield better milage.

...FYI: GASOHOL is basically E15 (15% ethanol+85% gasoline).

My results agree - around 10% worse FE with 10% ethanol.

Bums me out because I used to be a huge supporter, thinking, "we could use 15% in every gallon we sold, displacing money we were spending on oil into money spent on corn, etc." But now I just wish they would put 100% gas in and charge me 10% more, or just put 10% less in my tank. Why make/use it - making it contributes to fossil fuel emissions, and on my car at least, doesn't even push it down the road.

I guess I do see one reason to use 10% - then they can sell 90% ~84 octane gas to you with the ethanol to boost octane to 87.

^ That's another reason my car runs like poo on E10. The 3800 is designed for straight 87 octane, not 84 octane blended with ethanol to make 87 octane. My car is pre-ignition prone on low-quality 87 octane, so it pulls lots of timing to combat the pre-ignition. Every degree of timing it pulls is ~5 hp lost, so 8-10 degrees of timing pulled is 40-50 hp lost just above idle, when it pings the worst, and isn't making much power to begin with. So the computer dumps more fuel to compensate for the ping, and voila, worse fuel economy.

The best part is that corn ethanol takes more energy to produce than it contains.

I've noticed a 12-15% drop with E10, so have my parents who drive the same route every day and for a while made a note as to what kind of gas they put in, the pure gas tends to cost 3-5% more and you get better mileage... and use less gas then if they left left the alcohol out all together!
read up on alcohol engines some time, alcohol engines and gas engines are about as close as gas and diesel engines, sure I've mixed bio-diesel in with my gas and that worked but I'm not sure if it was really worth it, if I used less gas, but I was running a bio-fuel.

The epa ratings for E85 and Gas on flex-fuel vehicles very closely match the theoretical loss due to the lower energy content of ethanol. Following that same math for E10, you get a 3% reduction.

Example: 2009 Ford Crown Vic
Gas: 16 city / 24 highway
E85: 12 city / 17 highway

GASOLINE lower heating value: 116,090 BTU/gal
ETHANOL lower heating value: 76,330 BTU/gal
E85 = 82,294 BTU/gal
82,294 / 116,090 = 70.9%

16 mpg * 70.9% = 11.34 mpg
24 mpg * 70.9% = 17.0 mpg

Do you have the same engine my dad does?

If your dad has a 97 to about 2005 Impala, then I may have the same engine and transmission in a different chassis. 3800 Series II engine and 4T65 transmission in my car. The Impalas were either the 3400 or the 3800. The 4T65 can bolt to either.

Check the engine. If your dad's car has a black plastic upper intake manifold, it's a 3800. If it's flat aluminum stamped with "3400", it's a 3400.

If your dad is managing about 26-27 mpg highway with a 3800-powered Impala, that's about what a W-body gets.

He has the 3800, the bigger of the two. He gets 28mpg or so according to the on board thing, I'm not sure what he gets IRL. So is ethanol not effecting him?

It's affecting him just like all other 3800 owners who buy ethanol-laced gas. The people I heard 26-28 mpg from all live in E10 areas, and run whatever is the cheapest. Most of them also like hard acceleration and fast driving. I'm pretty sure his shift tables and engine tune are responsible, because my car gets ~32-33 mpg at 68-70 mph. Same engine and transmission, different computer settings and different chassis.

I found a non-ethanol station nearby so I fuel there. Every time I go home to NY state, which is mostly E10, my mileage drops 2-3 mpg.

Gas is only 2.25 for regular here. (e10) Gas (100%) is 2.59, doesn't really make sense.

The heating value of denatured alcohol is roughly half that of unleaded gasoline. The more alcohol in the blend the lower the power and mileage the unmodified car has.

I say unmodified because E85 has 100 octane and can tolerate much higher compression and spark advance than RUG - both beneficial to engine efficiency.

I avoid it like the plague.

Some drag racers run some insane timing on E85. They also have two tunes, one for E85 and one for 93 octane.

Madison, around me, the E10 can be had for $2.19. E0 is $2.39.

Around here, straight gas is $2.39 while E10 is $2.35. Clearly worth it for me, with a 3% improvement. (both theoretical and measured in my car)

My own personal experience last summer (in my Miata, not the Civic) was on a road trip to Montana I could TELL when I hit the stations without E10 because my mileage went from 28-29 to 33-34 and I was driving more aggressively (we are talking 3rd gear runs to redline while passing on several occasions). 34 was actually my new record for the car.
BTW, the car is an 03 and runs on premium, which might even have more of an impact.

My initial goal for the Civic is 45 (old EPA highway number) and I think it's going to be tough to hit on this E10.

So after running an entire tank of straight gas, the results were not surprising. 30.5 MPG. He usually gets 28 or so, so this is right at 10% reduction. And dare I say it seemed...faster?

I take that back, he ran a tank of E10 out this week...

24mpgish for E10
30mpgish for E0


HUGE jump in MPG.