Quote:
Originally Posted by 30 Closed Cab PU
I do understand the W for a 10W40 multi viscosity oil, 10W is for Winter.
I thought when you are talking about a single oil like the old SAE 30 ford oil, it was called weight. 30 weight, oil that is not modified. If not referred to as weight what is the proper term for it?
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Before the addition of the"W" designation, oil was catagorized by its SAE number (usually abbreviated as No.). For example, S.A.E. 10 or No. 10, etc. The term "straight" was also used; as in "Straight 10".
As refining methods improved, it became possible to produce an oil that had identical hot viscosity as No. 10 oil, but would flow at a lower temperature than 10. S.A.E. created the "W", or "Winter" designation (10W, 20W, 30W, etc.) for these oils. You can find charts online that give the temperature ranges for each viscosity.