Here in ontario , mcewen stations have had 15% ethanol for several years. I can see no difference in mileage in my commuting car(2001 corolla)which has 430,000km and counting. Exhaust is original and plugs when changed at 250000km still looked like new. Putting in new plugs made no dicernable difference. I record mileage at every fill... and as of 2yrs ago have spent more in gas than I paid for car new.