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shadrach74 · 03-14-2013, 07:30 PM

What flavor said is absolutely true. Also I would add that the XXW number is a measure of of how the oil flows (or doesn't flow) at a 100df. The -XX number is a measure of how oil flows at operating temp 212df. So 10w-40 and 0w-40 perform (read flow) quite differently at 100df, but exactly the same at 212df. My primary concern is start up lubrication. Which almost no oil does adequately.

While I use Blackstone for analysis on several vehicles and enjoy their plain speaking way of explaining each annualized sample, the are still measuring trends.

There is no logical reason I can think of to run 15W multigrade in a water cooled engine with modern tolerances unless those tolerances have widened to such a degree that it is required to maintain pressure. Even if i lived in Phoenix, I'd not be running
15w-XX. At colder temps, much of an oil of heavier XXw is likely pushed right through the bypass.

03-14-2013, 07:30 PM	#16
shadrach74 Registered User Join Date: Jun 2012 Location: Frederick MD Posts: 658	What flavor said is absolutely true. Also I would add that the XXW number is a measure of of how the oil flows (or doesn't flow) at a 100df. The -XX number is a measure of how oil flows at operating temp 212df. So 10w-40 and 0w-40 perform (read flow) quite differently at 100df, but exactly the same at 212df. My primary concern is start up lubrication. Which almost no oil does adequately. While I use Blackstone for analysis on several vehicles and enjoy their plain speaking way of explaining each annualized sample, the are still measuring trends. There is no logical reason I can think of to run 15W multigrade in a water cooled engine with modern tolerances unless those tolerances have widened to such a degree that it is required to maintain pressure. Even if i lived in Phoenix, I'd not be running 15w-XX. At colder temps, much of an oil of heavier XXw is likely pushed right through the bypass. Last edited by shadrach74; 03-18-2013 at 03:46 AM.