what kind of oil you use in youre onans in winter? i been running this http://www.amsoil.com/storefront/ase.aspx
but am wondering if i should be going to a 5w30 or 5w20 in winter. i run 5w40 in the hydraulic system. our winters here do get cold
I'm a believer in lower viscosity is better. Most people know that 90 to 95% of engine damage is done at startup while waiting for the oil to warm up and start flowing properly, but they will spec. their oil for that one time a year when you just got to mow the grass and it's 98 deg., 36 deg. for you Canucks. 0W oil is too thick at 70 F. to flow correctly at startup. I use 0W-30 synthetic in my X304. Much of the recent research with newer oils show that lower viscosity oils actually lube better even at high temps. This is why Toyota and Honda have lowered their oil viscosity recommendations, My wifes 2009 Honda Accord recommends 0W-20 oil.
I realize your Onan is not a new tight engine, but once warmed up the 0W-30 behaves just like any other 30 weight oil.