Non-alcohol gasoline = better FE.

[MadisonMPG]

Originally Posted by 99LeCouch

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?

[99LeCouch]

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.

[MadisonMPG]

Originally Posted by 99LeCouch

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.

[Big Dave]

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.

[99LeCouch]

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.

[PaleMelanesian]

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)

[96HX]

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.

[MadisonMPG]

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?

[MadisonMPG]

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

24mpgish for E10
30mpgish for E0


HUGE jump in MPG.