When driving, and when heat is on, smells like gas. But smell went away after air filter was replaced at oilchange. The gas smell seems to be slowly revealing

Hello, I don't think the air filter has anything to do with it. Did the cabin air filter get replaced also? Even then, a fuel smell is likely due to some kind of unexpected fuel leak somewhere underneath the vehicle, and the climate control system just naturally allows and introduces that odor into the vehicle. I'd recommend an inspection as soon as possible to see if there is a fuel leak, or a fuel vapor leak. This is important, as it could be a fire hazard. www.repairpal.com/repair-shops