Sudden (apparently) decline in gas mileage?

[BigSwede]

Well this is the first winter with E10 (where we didn't have a lot of snow). With all the warm weather, people should be seeing higher avg MPG than E10 might dictate. (FWIW, if you didn't know: Alcohol returns less energy (BTUs) for a given combustion cycle. So, there's no way we'll get the same MPG as the 100% gasoline days.)

It's not as big a difference as you might think.

Ethanol contains roughly 80% of the btus of gasoline. So if the mix is 10% ethanol, you still have 98% of the btu as before. So you can expect 2% less btu and hence, mpg. So if you were getting 16 mpg before with straight gasoline, it will "plummet" to 15.68 mpg with 10% ethanol.

[89Vette]

It's not as big a difference as you might think.

Ethanol contains roughly 80% of the btus of gasoline. So if the mix is 10% ethanol, you still have 98% of the btu as before. So you can expect 2% less btu and hence, mpg. So if you were getting 16 mpg before with straight gasoline, it will "plummet" to 15.68 mpg with 10% ethanol.

I understand your point....I'll have to go back and refresh on that one. Thru the vette forum, I'm a long-distance friend to an injector rebuilder/seller. He figures a 5% change (drop in mpg) due to ethanol. He's got a micro-drilling rig and injector response machine. Both were purchased to design "in-between" injectors as replacements.

For example, a car the came with a 22lb/hr injectors will be fitted with a 23lb/hr injector as an ethanol replacement (to maintain stoich balance). The mapping machine helps him determine/compensate for non-WOT fuel delivery.