Regular or high test gasoline

I tracked mileage on my 27' Class C with a Ford V10 on various brands of gasoline for several years. I consistently got better mileage using top brand names like Shell, Sunoco and Exon. I could never get the same mileage using discount brands like Murphy, etc. I will admit if you take the price difference into account with the mileage, it might work out about the same overall cost.

My Ford V10 never pinged on anything, but octane doesn't seem to affect mileage.

So, what's different about discount brands. Not sure - maybe the fuel is older? I know gasoline has a short life, as far as top efficiency. Some say there's no difference and even come out of the same delivery truck - yeah, right. All I know is my tracking showed there is a definite difference.

Or maybe the discount brands are more likely to have ethanol. Ethanol will definitely lower mileage. Just about any brand, even top brands, come with and without ethanol. It's up to the distributor/station which to sell. Most states require a sticker on the pump, but they have a way of disappearing.

Best bet for top mileage is to buy top name brands without ethanol - if you can find it or even care anymore...