Some years ago when everyone was throwing a fit about E10 fuel, I decided to test out the differences between E0 and E10. I did it to prove a point to my brother that E10 was a weaker fuel than E0, and I tried like crazy to get that result.
Test car was my '92 Mustang with a 347ci SBF, AOD transmission, and 9" rear end. I tried 93 octane E10 and 93 octane E0.
On the dyno, making multiple pulls to tune the car on each fuel, it made a hair more power (+2 hp, +4 tq average) with E10. This was with both tuned to 12.5 air/fuel ratio and 36 degrees peak spark advance. Coolant temperature, oil temperature, and transmission temperature were all kept constant.
At the track, I noticed the same thing. The E10 fuel was slightly quicker.
I wanted to prove the fuel economy theory so I tested both fuels on a drive of 250 miles down I-20. The tunes for both fuels were at 15.0 air/fuel ratio at part-throttle cruise with spark advance at 40-42 degrees. Similar weather conditions, steady at 65 mph down the same 250 miles, the 93 octane E0 netted 2.7% better fuel economy. However, it cost me 11% more at the pump so that was still a net loss in my book.
I also took two old carburetors I had sitting around, filled the bowls in one with E0 and the other with E10, and let them both sit for 6 months. I didn't observe any sort of gunking or other buildup in either one.
From that point on, I just put the cheapest E10 93 in the tank I could find and drove on.
