On engine oil marked 5w-30, why is the latter number higher than the first. According to engine oil manufacturers sources, the numbers indicate viscosity. 5W indicates a cold engine (winter) and 30 at normal operating temperature. But the viscosity of oil drops when heated, so why is it a higher number?
In: Engineering
The way this type of oil works is that it has additives that stabilize the viscosity of the oil. At lower temps they resist the natural thickening of the oil, while after it heats up, it resists the thinning effects of heat. 5w-30 is a fairly common oil used for northern-ish areas that have winter but also get hot summers. Go further south to areas that are warm year round and you’ll see people using things like 15w-40 or even 15w-50.
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