>>>*To understand which oil to use, think of it this way.

A 10W-30W designation means this. When the oil is cold, it flows at the same rate as a straight 10W oil.

When the oil is hot, it flows at the same rate as a straight grade 30W.

Between oils, this does vary a touch, not much. I run 10W-30W year here in Oregon, until the rig gets lots of miles, then I run a straight 30W. In extreme low temperatures, I would consider a 5W-30W.

In racing engines, we would run 20W-50W because of added oil clearences and the oil temp gauge often being pegged at 300? plus...Synthetic, of course....*EB