Actually, my mom is using reg. in her volvo instead of e10 (not 15 like I first mentioned) because she noticed a 10% increase in FE after switching. Right now reg. is .10 more expensive, but it would have to go over .26 more expensive to financially not make sense (fuel is currently 2.59 here) if my calculations are correct.

I am still interested if anyone knows what the emissions differences are. Does e10 just reduce all emissions by 10%, I kind of doubt it.

...most likely a donkey, but if he had to drive a car, i bet it would be a hybrid.