The engines!

Air-cooled generators come with engines that use fans to force air across the engine for cooling, while liquid-cooled generators use enclosed radiator systems for cooling, similar to an automobile. Generally, liquid-cooled engines are used on larger kW generators due to the larger engines required for the higher power output.

How does the Generac OHVI® engine compare to air cooled engines used in other brands of standby generators?

Unlike other engines used in backup power generation, Generac OHVI engines are made specifically for generators. They are engineered to run for the long periods of time required during a severe power outage or on a job site, utilizing the same type of pressurized oil lubrication used to give automobile engines long and trouble-free lives.