Hi, up here in Manitoba, Canada, our gasoline contains ethanol. The low grade contains a lot, just how much, I do not remember.
The Government decided to use food for fuel, one of the more stupid things to do.
Anyway, ethanol has less BTUs, or less bang for the buck. The gas mileage on my Jeep Cherokee went from 28 miles to the CDN Gallon to 20. Same thing happened to my Porsche 944, until it burst into flames, split FPR
I have a new to me RX7 88 'vert, which I like a lot. Someone told me that premium gasoline here does not contain ethanol, so I tried a tank, and in my case the 88 ran smoother and the gas mileage seemed to be improved. So I'll try another tankful before I put her away for the winter and check the mileage, in any case I don't want water-attracting fuel in the system over the winter, as the car will sit until late March.
Any comments, folks?
Mike

 

Your 88 RX-7 is only rated for up to 10% ethanol (E10). Your car should not have run any smoother with premium unless the engine is tired and needs a rebuild soon. I am not familiar with your various Canadian blends, but I would imagine that the premium grade would have ethanol if the regular and mid grades from the same vendor have ethanol.

Yes, ethanol has less energy content, but E10 should not have dropped your Jeep's mileage that much. You should calculate the mileage by filling the tank all the way, resetting the trip meter on the odometer, and then checking to see how much gas it takes to fill it up for the mileage driven. The test will not work well if there is a large change in temperature.