My main "car" is a 95 ch*vy Tahoe 4x4 with towing package.
It was getting around 10-12 MPG around town lately when I
saw a newly available fuel around here called "E-85"
which is 85% ethyl alcohol and 15% gas for a net octane rating
So I started the inner wheels churning and came up
with a plan, I would try about 10 gallons and see what happened.
I knew the 105 octane could tolerate a good bit more timing but
would it need more timing? I believed it would need more and I was right.
Stock timing is 0* (TDC) because of the heavy truck and 87 octane,
I have not had a timing light on it yet but I think I have added 10*
or more timing total. Now I think it needs more idle speed, sometimes
it dies but overall I believe it is getting better mileage (!)
feels like it has better torque. I can accelerate w/o downshifting more often.