Quote:
Originally Posted by gravitylover
If that's the case then why do I get better mpg and why does the car run cooler on non ethanol fuel? It might be because our fuel pump runs cooler on non e fuel so it is more efficient. For straight interstate running 10% ethanol does give me slightly better mileage but for twisty, hilly back roads with small towns mixed in non e is far superior.
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Non-ethanol gets you more MPG because there's more potential energy per volume of gas than 10% ethanol gas. This means under normal driving conditions, you'll be on the gas less.
Ethanol gas is more knock resistant than non-ethanol. So under high loads (e.g., wide open throttle), the gas will burn cooler, therefore, reduce knock. This is exactly why tuned engines can make a lot of power with E85.
The stock engine/tune will knock with 91 gas, which means you'll lose a little bit of power. The owners manual even recommends 93 minimum.
Also non-ethanol 91 will cost more than 91 ethanol, so your MPG gains are moot point.