[JackDidley]

Originally Posted by lkchris

Well, I once checked the specs for Mobil 1 ... 0W, 5W, and 10W all had the exact same cold pour point (-55F)

The only significance of the W number is related to how the oil flows at a cold start ... after that (after warmup), it's meaningless.

In addition, because this is full synthetic, there is no need for a lower number oil for winter, as a warmed up motor is a warmed up motor, regardless of ambient temperature. With full synthetics, the only real significance of 30, 40, or 50 is engine clearances and engine friction. For an old aircooled engine, built with looser tolerances, 50 is good, new water cooled motors are being built to tighter and tighter clearances these days, so much so that xW-20 or even XW-16 oils are specified. What ever is specified is good year around for full synthetics. If you're using Porsche A40-spec oil (as you should) it's full synthetic.

There are guys on forums that will argue all day that one has to run 0 -? weight oil. Anything else will kill your motor. It has to be true, they read it on the internet.