How the hell have you not gummed up your mower's carburetor with ethanol gas 3 years old? In general most cars are made to run on ethanol fuel, while small engines will have the most trouble with it. However, the breakdown is a very slow process, maybe your car still starts after 7 months sitting but could be getting buildup of sludge and just not notice it for 12-24 months. After all, there are a lot of little old ladies who barely drive their cars once a week. I just like to keep my engines really clean so I don't take the risk.