What Is the Difference between 10w30 and 10w40 Oil?

Answer

The difference between 10w30 and 10w40 oil is the thickness or viscosity of the oil. At cold temperatures or when an engine is cold, both of these oils operate the same. But at higher engine or environmental temperatures, the heavier oil, the 10w40, operates better.
Q&A Related to "What Is the Difference between 10w30 and 10w40..."
Most cars call for 5W-30 or 10W-30, but if you are in warmer
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With any multi viscosity oils the first # represent the viscosity(thickness) at start up temp. The second # represents the viscosity at operating temp. The smaller the # the less
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The numbers in a name like 10W30 refer to an oil's "weight. This is a measurement of the oil's viscosity - how thick it is, and how quickly it moves. Lower weights mean a thinner
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10W30 would be used in cold climate. 10W40 would be used in hot climate. 30 and 40 means the thickness viscosity when warmed up.
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