I've been running straight ethanol free car gas in my VW powered plane, but on a recent trip wound up having to put some AVGAS into the tank to give me a comfortable edge in the amount of fuel I had for the trip home.

I didn't notice any real difference in performance, to be honest - perhaps it's to subtle for the type of flying I do. Fuel burn seemed about the same as well; it might just be my imagination but it looked like I burned more 100LL than I would have gasoline. One fifty mile trip isn't a good gauge at any rate, as I rarely fly consistently on any given leg.

Indeed, I'm not all that interesting in benefits, as in my high drag very slow aircraft there's a diminishing return on performance gains.

The larger question is one of running 100LL causing problems. I'm thinking that I probably won't have any issues with lead gathering on the spark plugs, etc., as it's occasional and in a mix anyhow.

A few facts:

1) I operate at low altitudes - no more than 4,000 feet above sea level (well, with density altitude figured in we can add 2,000 feet to that in summertime. ).
2) I may operate at freezing temperatures once or twice a year...the rest of the time it's temperate or downright hot here in Alabama.
3) It's a bog standard Volkswagen engine with a bog standard Holley carb, with the fuel being pushed through a bog standard Facet electrical fuel pump.