Quote:
Originally Posted by rmay635703
Not to push you in an alternative direction but on my cobalt which has a 10+:1 compression ratio motor, seems to have a sweet spot above plain 87 octain, it also coughs, bucks and chugs less at low RPM with mid grade or higher.
These cosmetic differences brought me to wonder if the higher octane of e85 and slightly lower cost would have a break even point for cost vrs fuel economy.
I tested several tanks two were with 87 octane (ethanol free) with 10-20% e85
This mix was a net savings because at the time the ethanol free was only a few cents more than E10 and the e85 was cheaper, fuel economy was about 2-5% better than expected but within noise. (but also cheaper per gallon.
I also tested 93 octane e0 mixed with 30% ethanol (e85) because it cost the same per gallon as e10 87 in this mix, and I could not find e0 87 anymore. This tank was moot (matched FE) and there was no cost savings but the car ran better in specific situations (aka low RPM) and seemed a tad peppier.
So yes you can get slightly better FE with better octane or you can use e85 and get premium like fuel at a slightly better price point without a fuel economy hit. (if you find your cars sweet spot)
Good Luck
Ryan
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I can definitely try mixing E85 with regular fuel; unfortunately to my knowledge there are no straight-gas stations in my state.
I have 10.8 compression ratio--my engine definitely sounds "smoother" with high-octane fuel (I noticed that when it was ~90% premium). I'll try the high-octane route first, then try mixing E85.