Raw fuel can cause problems as well as exhaust residue (burned fuel).

I have seen damage to painted finishes when not allowed to cure before use. I ues Rustoleum over 21st Century Fabric. It dries in 24 hours (won't stick to your finger when touched) however it takes 2 or 3 weeks to cure (harden and attain maximum resistance). I used lacquer to finish furniture. It "dries" in less than 30 minutes and takes over 6 weeks to cure!

If the burned fuel damages the paint the raw fuel will do it faster.
It has more to do with what paint you use rather than the fuel (unless using 40% racing fuel). As bob_nj says above it is better to use covering (monocoat or ultracoat etc).
Bill