how much performance difference e85 to e80?

[12gt500]

i just tested some local e85 and it came out to e80. i don't know if it is still a winter blend here in marietta ga. but i was wondering about to get my engine built and tune from lund on e85. but since my local fuel is testing e80 at this point. ho much difference will i see/lose from the e80.

i am using the quick fuel glass e85 test tube.

 

[70SCJ]

You will want your tune to be for E85. That way when your winter blend starts you will be just a little richer. If you tune for E80 and then run E85 you will be leaner and depending on the aggressiveness of the tune you could be in trouble.
Power loss from E85 to E80 is most likely negligible.

 

[Shadow Grey 03]

You will want your tune to be for E85. That way when your winter blend starts you will be just a little richer. If you tune for E80 and then run E85 you will be leaner and depending on the aggressiveness of the tune you could be in trouble.
Power loss from E85 to E80 is most likely negligible.

Came in here to post this. Couldn't have said it better :beer:

 

[mach330]

E80 and E85 will make virtually identical power. There are big gains to be made from E0 to E50, after that... Not so much.

As far as running rich or lean... Don't worry about that minor difference in ethanol. Remember pump gas can be 0% or 10% ethanol, no big deal. Same with higher contents. If you tune on E80 and run E90, you will be slightly leaner. E70 will be slightly richer. Ethanol doesn't knock the same way gas does. Running lean on E85 is less dangerous than running lean on pump gas. Unless you are on the ragged edge, don't worry about it. And if this a street tune and you are that worried, find a new tuner.