Self Service Avgas (100LL) is available 24/7, at two pumps at the Airport Terminal. Check KGTU fuel prices at airnav.com/fuel/local.html.
Full-service Avgas (100LL) is available through the FBOs.
Full-service Jet Fuel (Jet-A) is available through the FBOs:
The Airport does not have self-serve Jet A fuel.