I use diesel oil (Rotella synthetic) in all my non vehicle engines. It has additives the car oils don't have because of the catalytic convertors potential of being contaminated. During the very cold winter camping season I use 0W-30 Mobil 1 because the generator will shut down on the first few starts due to oil warning light with the more viscous oil I use as recommended in the summer. The 0W is thin enough in the very cold that it doesn't cause that problem.