Synthetic oils came up in this forum a while back. I thought i would add my two cents about this subject. If you plan on only using your generator a short time, or have it in storage, synthetic oils may not be the best choice. Synthetic oils are way too slippery and leave a thinner film on the metal parts. if it takes longer to start your engine after sitting for along period, the moving pistons will remove the protecting coating on the cylinder walls. Also, how often does the manufacture want you change the oil? if every year, what's the point?
Another thing, the engine is air cooled only on it's cylinders, the rest is oil cooled. A good mineral oil will keep it's film on the metal parts much longer after the engine is shut down.
Bob and Kate Weigant
Elite 2006 36TK3
2007 M2 Freightliner
In a land of the blind, the one eyed guy is king.