Quote:
Originally Posted by Ecky
You'd need to gain around 33% more economy to make up the BTU difference with E85 vs gasoline (though I'm sure it's cheaper per unit volume). I've personally found gearing to be much lower hanging fruit, and lean burn to be more for the last few percent.
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This really depends on the car, sometimes mechanical friction is the main source of inefficiency (taller gearing helps more), but other times it could be low combustion efficiency or high throttling losses.
Mechanical friction reduction from taller gearing has diminishing returns. If you have like 50-60% mechanical efficiency like my car at cruising conditions, slightly taller gearing drastically cuts down the friction and raises mechanical efficiency a lot. If you're at 80%, the gains are much much less, probably far less than half.
On cars with engines that are tasked with higher average loads, lean burn can be a tremendous help.