Oil Change

[cycleguy55]

Originally Posted by bobcowan

That might not be the best advice for a Windsor engine.

At 0*C, a 15w-50 oil has a viscosity of 1328
At 0*C, a 0w-30 oil has a viscosity of 475.

During a cold start, I would certainly want the lower viscosity. Get that oil up and moving as quickly as possible.

As for a 50 weight oil, a well built Windsor just doesn't need it. It should easily be able to maintain proper oil pressure with a 30 weight. The viscosity difference at 100*C is about 80%. It takes energy to move that extra thick oil around.

Not many of us start our Cobras at 0°C, though I must admit I have started mine at temperatures not much warmer than that. Your point on lower viscosity at startup is well taken, however. The previous owner of my car advised me to use 20W50 (probably because of the various leaks), but I switched it to 5W30 and it seems quite happy. I get 70-80 PSI on cold start fast idle, and hot idle is about 25 PSI. Now that I've fixed the most egregious leaks (sucking oil past intake gaskets, upper half of main seal installed backwards, bellhousing bolt into engine valley not sealed) my oil consumption is WAY down, even with the 5W30.

BTW, not only does it take more energy to move thick oil around, it's also a lot harder to get proper lubrication in fine clearances with a 15 or 20 weight oil than a 0 or 5 weight oil. As many have written, the majority of wear occurs on startup, and a thinner oil provides GREATER protection due to its ability to flow into those narrow spaces.