kpmartin@watmath.UUCP (Kevin Martin) (09/26/84)
>I was suprised by a recent statement made asserting that a multi-viscosity >oil got MORE viscous when cold. I assume that was a typo or perhaps someone >can correct me. Ok. I haven't seen the original article, but I assume whoever wrote it wanted to say: *For a given grade of oil*, that particular oil will be thicker (== MORE viscous) when it is colder. Viscosity is an measurable quantity, and varies for any liquid as temperature changes. For motor oils, the word 'viscosity' is often used for the 'grade' (e.g. 10w30), which is a different matter. In this case, one would say: *For a given desired viscosity*, you need a lighter grade when it is colder. I think this is what you understood. The whole idea behind multi-viscosity (read multi-grade) oils is that their viscosity is the "correct" viscosity over a larger range of temperatures than for single-grade oils. Multi-grade oils come in several ranges, in fact, e.g. 10W30 spans a smaller temperature range than 5W40. Kevin Martin, UofW Software Development Group.