Air-cooled engines are designed with looser tolerances for the block and rings to accommodate heat fluctuations. Consequently, these engines tend to consume more oil for cooling and may experience some blow-by in the rings. With changes in automotive motor oil formulations, it's no longer advisable to use such oils in air-cooled engines.
So, what changed in automotive motor oils? Well, the permissible levels of Zinc and Phosphorus were halved in 2010, following earlier reductions. This decrease diminishes the oil's thermal conductivity and anti-wear properties. Air-cooled engines are particularly affected by this alteration because they rely on motor oil to dissipate heat and cool the engine.
Air-cooled units will inevitably consume oil, and it's recommended to shut down and check the oil every 24 hours. The quantity of oil used depends on the type of oil you choose. We recommend using 5W-30 full synthetic oil specifically formulated for air-cooled natural gas/propane units, as it minimizes oil consumption more effectively. The amount of oil consumed will vary based on the load and the type of oil in use. It's not uncommon to observe half a quart being used in a day, especially under significant load volumes. Therefore, it's essential to check the oil daily when the generator is under heavy usage. For further information, refer to this article: What Kind of Oil Do I Use?