Generac recommends the use of 5W-20 full synthetic oil for all home standby generators, but owners can also use SAE 30, 10W-30, or 5W-30 synthetic oil. The right oil handles high temperatures, resists thermal breakdown, and offers excellent protection during frequent startups and prolonged operation. Below is a summary table. This article provides guidance on the oil requirements and maintenance tasks for Generac air-cooled home standby generators. Different generators call for specific oil blends, and the right formula can extend the lifespan of your equipment. Using the right oil helps reduce engine wear, manage heat, and.