I find that I get better fuel economy when using the unblended gas, i.e., no ethanol. This was before ethanol got to be the big issue it is today. On the other hand, my '69 (bought 6 months later), also equipped with a 350/TH400 would run fine on regular. It took premium gas to keep it from running-on, or from pinging under acceleration. It would run on, when you shut off the ignition. That truck would bark the tires everytime it made the 1-2 shift, if you had the least amount of foot in the throttle. It had a hot little 350, that also had a TH350 behind it. Now, for the issue: the first '69 C-10 I bought was back in '99. Since I went to unblended gas, no more problems with squirrels. Here's another: the ethanol attracted squirrels to the gas tank on my Honda mower.squirrels chewed a hole in the tank to get to the fuel. The ethanol attracts moisture, contaminating the gas in that equipment with water. This is the first season that I have done that. At the same time, it is better for outdoor equipment (mowers, chain saws, etc.) to run ethanol-free gasoline.
It is done to cater to the boating community. Where I live, there's one station that sells unblended gasoline.
