10W-40 vs. 10W-30 motor oil.
04-01-2005, 05:19 AM
#2
Re: 10W-40 vs. 10W-30 motor oil. (eg62come)
It's sorta like viscosity, but with a difference. People traditionally talk about 'weight' of a motor oil. The numbers 10, 30, 40 are oil 'weights'.
A 'standard' 30 weight oil means it has some particular viscosity at 100 degrees C. A 40 weight oil has higher viscosity. I'm too lazy to look up what that viscosity really is, in true units of viscosity.
Winter 'weights' are measured at 0 degrees C, but the viscosity scale is completely different. That's the weight followed by 'w'. (The 'w' means winter, not weight.)
A 5w-30 oil has to have the right viscosity measured at 0 C to satisfy the spec for a 5w weight oil. But when you measure it at 100 C it has to match a 30 weight oil.
Check out http://www.bobistheoilguy.com for enough information to make your head explode.
A 'standard' 30 weight oil means it has some particular viscosity at 100 degrees C. A 40 weight oil has higher viscosity. I'm too lazy to look up what that viscosity really is, in true units of viscosity.
Winter 'weights' are measured at 0 degrees C, but the viscosity scale is completely different. That's the weight followed by 'w'. (The 'w' means winter, not weight.)
A 5w-30 oil has to have the right viscosity measured at 0 C to satisfy the spec for a 5w weight oil. But when you measure it at 100 C it has to match a 30 weight oil.
Check out http://www.bobistheoilguy.com for enough information to make your head explode.
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