you want a small town airport that has prop planes..most of those still use 100LL Avgas. Very stable and consistent from batch to batch They have to run it because the carbs are certified to use it and to recertify is a major hassle..Break down in mid air its a big deal..no pulling off the side of the road at 3500ft in the air. Its not illegal to sell it to you, for off road use anyone can buy it..just dont put it in your tagged road vehicle. I don't have a plane, I just know the people that run the airport, been buying gas there for 20yrs. I guess if you can't find Avgas, then VP or Cam2 fuel would be the next best thing..I think Jegs.com offers it.
