America's love affair with gasoline continues to defy every logical argument against it. That's because it presents the path of least resistance. For many, that's the most compelling argument to stick with tried and true unleaded gas.
Convenience is one of the main benefits of using gas in a lawn mower. There is no shortage of fuel stations, so filling up can be done on the way to the first job of the day, between jobs or whenever you have a few minutes to spare. Taking your personal car to the filling station? Bring along an extra couple fuel containers and fill them up at the same pump.
Gasoline engines aren't as low maintenance as your other options, but most small engine repair shops only work on gasoline engines, so it's easier to get service when you do have a problem. If you happen to know a thing or two about engine repair, it's most likely a gasoline engine.
Investment wise, gasoline powered commercial zero turn mowers have the lowest up-front cost. New EFI (Electronic Fuel Injection) engines, such as the ultra efficient Vanguard™ 810cc EFI found on some Ferris lawn mowers, continue to supplant carbureted models. They offer increased engine efficiency and reduced service intervals, making gas less of a compromise.
For many commercial lawn care operators and large acreage home owners, unless there is a demand for one of the other fuel types, simplicity may win out.