Thread: 30w verses 50w

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As I'm your Uncle I feel compelled to attempt to save some of you embarrassment.

There is no such thing as 30W or 50W...........the specification for winter viscosity grading (what the W represents) stops at 25 grade for crankcase oils.

Originally Posted by Bob Parmenter

As I'm your Uncle I feel compelled to attempt to save some of you embarrassment.

There is no such thing as 30W or 50W...........the specification for winter viscosity grading (what the W represents) stops at 20 grade for crankcase oils.

Once again, Uncle is correct and I fell into the trap, too... Lots of people toss in the "W" as weight (30 weight, 50 weight) but it's actually a testing temperature reference and in the multi-vis oils the "W" goes with the lower number, i.e., 10W30 is an SAE graded oil that has been tested to prove that it acts as SAE 10 at colder temps, and SAE 30 at 210F (100C). This whole discussion highlights why straight grade oils are not the best choice for street use - they have not been tested at temperatures below the approximate operating temperature of your engine, they don't have the additives to thin them in colder temps, and their viscosity in colder ambients is not verified.