Is it a requirement to label the fuel type at each tank fill cap location? i.e. 100LL etc. If so, is it required for Experimental aircraft or just certified type certificates?
IIRC the legal short answer is no as it is a part 23 requirement. The practical, will a DAR/FSDO sign off on it is most likely yes. Here's a long thread for the details.
FWIW, I had my fuel caps engraved with my engine's min fuel grade, tank capacity and N number and I'd do it that way again if I had to do it all over again.
