Autogas/82UL STC's. Aircraft owners choose automotive fuel (mogas) rather than aviation fuel (avgas) for a variety of reasons. The primary reason is cost. The savings in fuel prices between auto fuel and avgas are quite significant. In an airplane using 15 gallons per hour, a savings of only 50 cents per gallon will be $7.50 per hour less than the cost of using avgas. In 200 hours, this adds up to $1500.00. Savings of even half this amount would clearly justify the installation of an auto fuel STC. If you use auto fuel, by the time you run an engine to TBO you will have come very close to saving enough money to buy the next engine.