Originally Posted By: bigsteve
Does 1 quart of mmo added to 10w30 engine oil change the viscosity numbers?
You live in Massachusetts, not like you are living in Florida, MMO added to the oil should help you out during the wintertime.
I have been using MMO with 5w30 motor oil all year round in an engine that now has 390,000 miles and all is fine, I have been doing this for 23,000 miles, if there were any problems then I would be telling everyone.