E-85 mileage in comparison to 93 octane gasoline.

[Fourdoordsm]

I switched over to E-85 at the beginning of march, and have some pretty good data built up including comparison to my fuel economy on 93 octane before making the switch.

My running average fuel economy on E-85 over the last 2765.3 miles is 17.648 mpg at a cost of $13.96 per 100 miles traveled. Worst fill up was after a bunch of WOT driving for tuning at 15.2 mpg and best on a long highway trip was 21.8 mpg.

My running average fuel economy on 93 octane gasoline over the previous 6712.8 miles was 21.23 mpg at a cost of $13.32 per 100 miles traveled. Worst fill up was after a bunch of WOT driving for tuning at 18.5 mpg and best on a long highway trip was 25.0 mpg.

This is the running average, along with worst and best for both fuels in my car with the mods listed in my signature. I do a mix of city and highway driving along with trips to the drag strip (19 passes so far on the car) and some aggressive driving on the street when accelerating.

Later,

Keith

[David Buschur]

The cars I tune on E85, and there are a lot of them. Generally require 30% more fuel for good E85 than they do over pump gas. I'd have assumed you'd see a 30% loss in fuel mileage.

Can I assume you've worked on the AFR's down low and are running them leaner than 14.7:1 (gas AFR's)?

[Fourdoordsm]

Actually I have not messed with the tune in the cruise range. I didn't want to mess with having my long term fuel trims maxed out so I didn't mess with it. By my A/F ratio meter I am running right around 14.5 : 1 most of the time at idle and when cruising.

The only thing I can think of that would account for the extra gains in fuel economy is switching to a light weight high performance wheel and tire setup. My winter wheels were lighter than stock, but snow tires are not known for their fuel economy... but now I am running on EVO IX MR wheels with stock Advans at 42 lbs on each corner vs the stock setup at 50.5 lbs per corner. So, all my driving on gasoline was on the heavy stock wheel and tire package, or on winter tires. Virtually my entire time on E-85 has been on the EVO IX MR BBS rims and stock Advan tires.

That is the only thing I can think of to explain why I am not getting around 16 mpg like I would have expected.

Later,

Keith

[vwjeff]

great thread as I have been thinking about this, I will post up what I am getting when my car gets here!