@dtmbinb Even at -20C my Oil pressure is fine with 10/40 Royal Purple HPS. There have been lots of reports ticking with 5 weight until the engines up to temp, regardless of outside temps. I suspect it just old tired engines, but it could be our type of oil pump too, no one uses eccentric gear pumps any more.

 

5w oil, The least protection just when you need it most.

 

I assume you are talking about on an old design motor like the Rover V8 due to the oil pump design? Plenty of high performance motors run 0w40. Porsche for one. Quality synthetics do in fact protect at start up, even in 0 or 5 weights.

 

Right, I'm talking about in the Rover/Buick V8 application.

 

Cold rating is mostly irrelevant when at operating temp, the difference in viscosity is negligible. Even 5W- oil is thicker at cold start than 20W- oil at a halfway warm engine.