Can anyone think of any way in which E15 could improve fuel economy?

[fdcg27]

Last tank of E15 I saw a calculated 58.1 mpg with the HAH, good but not unknown to me in past periods of warm weather.
Refilled yesterday with 9.9 gallons of E15.
Sixty miles into this tank, the car is showing 60.0 mpg and the car is almost always conservative in its fuel consumption estimations.
This gets me into pretty exceptional territory, especially since I would expect a minor loss in fuel economy with E15 88 relative to E10 87.
Could a one point increase in octane rating allow enough of a difference in ignition timing advance to provide a measurable imcrease in fuel economy?
Or, is this just a coincidental fluke with me getting interested in something that isn't real?
Curious what everyone thinks.

 

[atikovi]

Too many variables to account for such a slight increase in mpg. Slightly higher octane for more advance is part of it. A 10 mph tail wind would probably help even more.

 

[DriveHard]

change to summer blend gas, warmer temps, higher tire inflation pressure due to warmth

 

[Hermann]

The E15 88 octane is also a mystery to me. It many times has had better mileage 1-2mpb than the 87. Sometimes it has been a bit worse.

 

[slacktide_bitog]

Different driving conditions? More EV miles? There are too many variables in play

 

[71Chevyguy]

Every time I use it in my 2010 Elantra, it always gets better fuel economy, around 2-3 MPG better. But the owner's manual specifies never to use over 10% so I don't use it all the time.

 

[JohnnyJohnson]

NO

 

[Hall]

The MPG meter in my G35 always settles around 19.2-19.3 MPG after a while (I occasionally reset it if I'm making a drive on the interstate). My last 3 fill-ups have been at a new Sheetz location using their E15/88 octane and I just happened to check my current MPG and it's 19.9. My car also likes this fuel apparently. When I've used 87 in it, I could tell and performance was absolutely impacted along with pinging under acceleration. 89 was better but still not as good as 93. I just hope Sheetz keeps their E15 as low priced as they can for as long as possible (I know they won't....). They're keeping Speedway in check so far too !

The 19.2-19.3 is consistent too. This isn't a thing from winter gas to summer gas, in my case.

 

[Rmay635703]

The E15 88 octane is also a mystery to me. It many times has had better mileage 1-2mpb than the 87. Sometimes it has been a bit worse.

I’ve been burning e15 on and off since 2002.

My experience is that if it’s hot you get better than expected gas MPGs on e15

Cool or mild and it’s not as good, cold and I don’t recommend it unless you are running very hard since fuel economy drops slightly.

Back long ago when I towed heavy trailers fair to fair for a little business my oldish vehicles thermostat stayed cooler on e15 than e0


On my Volt which claims to require premium
e15 has lower knock counts than 89 octane

Don’t underestimate The vapor pressure and cooling effects of ethanol fuels which is good in summer and bad in winter


My old 1999 Honda Insight would hop and buck and skip during lean burn on e10 (octane didn’t matter)
Move up to e15+ and it ran smoothly in lean burn.

 

[spasm3]

I get a couple of mpg worse in the Elantra. 3mpg loss when towing with the ram.

 

[Invisible]

No, it's just cheaper.

 

[DriveHard]

In my Colorado I get about the same with E15 88 and ethanol free premium in the summer. In the winter, the E15 mileage drops ~3MPG. In the summer I get the poorest fuel mileage with E10 87 octane.

 

[fdcg27]

Well, we'll see what this tank averages out to over the 500 to 600 miles I'll run it.
After 110 miles, indicated fuel economy is down to 59.0, which is still higher than I would have expected under current weather and use conditions.
I can say that my initial concern in using E15 was that there would be a measurable decline in fuel economy with E15 but that doesn't seem to be the case.
I write the above with knowledge of the calculated mileage of every tank of fuel run since new.
I do have a pretty good idea of what to expect of the HAH under various weather conditions as well as the impact of higher RVP winter blend fuel on consumption.

 

[fdcg27]

Correlation is not causality, but this tank was 599 miles on 9.9 gallons, or 60.5 mpg.
This is only the third 60+mpg tank I've seen with the car.
Did the E15 help or hurt?
The most honest answer I can give is I don't know.