Motor Oil?

What does the W stand for in 10 W 40 motor oil?Motor Oil?
W=';Weight';. It refers to the viscosity of the oil (how thick it is).





With 10 W 40, the oil is blended in such a way that at normal temperatures it will behave like 10 Weight oil (very thin and runny) but as the engine heats up to operating temperature the oil will behave like 40 Weight oil (thick).





When an engine first starts the oil needs to flow quickly to bearing surfaces and parts. At cooler temperatures the 10 Weight flows faster.





When an engine reaches operating temperatures the heat causes oil to thin out; 10 Weight oil would not be able to protect the bearing surfaces from damage. But 40 Weight oil would thin out to the correct viscosity to lubricate and protect engine parts.Motor Oil?
it stands for winter Report Abuse

The difference between multi-grades and straight-weight oils is simply the addition of a viscosity improving (VI) additive. The most common grade of automotive oil in use today is the 5W/30, which is a mineral oil refined to the SAE 5 weight viscosity range containing the usual cleaning and anti-wear additives, then blended with a VI additive that should leave it reading in the SAE 30 weight range when at the higher (210F) temperature. The advantage to the multi-weight is, when starting the engine, the multi-viscosity oil has the thickness of an SAE 5 weight, which allows the engine to spin over more easily.





http://www.blackstone-labs.com/oil_visco鈥?/a>





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YOUR ANSWER TO YOUR QUESTION IS FIST OF ALL THEY ARE ALL WRONG THE W STANDS FOR WINTER
When selecting any motor oil the first number is the normal viscosity grade that the oil pours at in the W = winter. The second number 40 is the viscosity of the oil when it gets hot. These oils are multi-grade or multi-viscosity oils. No cars in the USA calls for 10W-40. New cars sold in the USA calls for 5W-20 or 5W-30. There are a few stragglers (cars) which still call for 10W-30- usually cars that are 8+ yrs. old.





The viscosity you should be using appears in the specifications paged in the handbook in your glove compartment. 80% of engine wear occurs during the first 10 seconds after start-up. Light weight oils pump to critical engine parts faster. It also cools the friction surfaces and block more efficiently than thick molasses oil. Because lighter viscosity oil (adsorbs) heat more efficiently. If you have never heard of the word adsorb it refers to the ability of a liquid to remove heat from a solid surface.
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