There's not only "top tier" in gasoline but also in Diesel fuel. Back in the 1990's one brand of diesel fuel started offering some additives added to their #2 refined vehicle diesel fuel in the Midwest area. It was called the "The No. 1 of diesel fuel" (not to be confused with refinery #1 diesel grade). The additives were to increase cetane rating, reduce the gelling temp level, and added an injector cleaner, and a much finer filtering which removed more of the impurities. The cost per gallon was the same as other plain diesel but users soon learned that this fuel did give better mileage and the stations were constantly busy at these additive diesel pumps compared to the plain diesel stations.
By 2005 a few other station brands were now doing the same in the Midwest area but the common name of " The No. 1 of diesel fuel" had become confused in people's minds with refinery No. 1 grade (quite different) so most brand fuel stations renamed it "Premium Diesel" here in the Midwest. We've very seldom seen the Premium Diesel name used in other areas of the country and when we ask about it the station's employees usually say "what!". Yes, you can tell the difference in MPGs when using premium diesel and it's all we used when it's avaliable when refueling where we are. Many of the RV haulers in northern Indiana insist on only using the the premium diesel brands and I've been told that by several.
It's one of the reasons we carry our 106 gal aux diesel bed tank (100 gal usable) when pulling the 5th wheel as we fill it at home and with our 34 additional gallons in the vehicle tank, we can go all the way to Florida from Michigan (over 1400 miles) and still have roughly 25 gallons left without refueling along the way. Done it so many times! Lets us pick and choose what fuel and at what price before we need to refil. Also a big plus as the farther south you go in Florida the higher diesel and gas prices usually are as they add a local county tax on fuel and sales taxes to rip off the visitors. Not only rips the visitors but also the florida residents as my Bro in the WPB area complains about constantly and he's far from poorby any stretch but doesn't like being robbed!
Yes, we only use a top tier gasoline also in our gas vehicles also and the difference is real and verifyable. Couldn't agree more with silvercorvette's thread post subject.