To my understanding all cars can be refueled in "All Cars & Tracks" menu. When I use "All Cars & Tracks" menu for Formula Classic @ Buenos Aires #15, I cannot refuel during race. From that group of cars(I checked each one) that can't be refueled in the single car series menu, only Formula Vee and Marcas can be refueled using "All Cars & Tracks" menu. I only play offline so I wanted the ai(and me) to pit at least once. The "PitStopStrategies" that I used to manually insert in the .gdb file somehow doesn't work anymore. So if I can't use fuel usage adjustment for us to pit, I opted to adjust tire wear = x3. My issue with this is the qualifying tires lasts only 2 laps during qualifying session. The only way I got away with a good time is to drive slow(2nd/3rd gear) on the first lap since it's not counted. Hopefully this will get fixed on the next update for "All Cars & Tracks" menu if indeed all cars can be refueled there.
Some cars such as the F-Classic had refuelling pit menu disabled on physics level, beyond series regulation parameter. We´ve changed that now so all cars just follow series regulation, which means you´ll be able to refuel with the F-Classic and other formula cars in the next public release.