SAE oil viscosity vs. Centipoise
SAE oil viscosity vs. Centipoise
(OP)
I have a viscosity chart that shows SAE 50wt engine oil viscosity varying from 175 to 280 cSt @ 40 C. Why is that? Also the chart depicts SAE 90wt gear oil varying even more at the same temp??





RE: SAE oil viscosity vs. Centipoise
At cold temperatures, oil viscosity can vary much more for a given SAE weight than at warm temperatures. You may not think 40 C is cold, and of course it isn't to a human. But, to an oil designed to operate at 125 C, 40 C is 'cold.' Depending on the oil formulation, two oils with exactly the same viscosity at 100 C might be very different at 40 C.
Gear oil and crankcase oil and manual transmission oil have different SAE weights for similar viscosity.
RE: SAE oil viscosity vs. Centipoise
As Xtrema says at the lower temperature of 40oC (as adopted by the ISO system, and in the US by ASLE, for all industrial lubrication fluids) and considering the different viscosity indices of these monograde oils, the spread in viscosities at 40oC becomes larger.
RE: SAE oil viscosity vs. Centipoise
I've got a chart that shows relative viscosity between ISO VG, AGMA, SAE crankshaft and gear - don't remember where it came from, but I can email it to you in Word format
send me your email address if you'd like it.
Keep the wheels on the ground
Bob
showshine@aol.com
RE: SAE oil viscosity vs. Centipoise
Can't keep the wheels on the ground.
klyde
sfkf@iwvisp.com
RE: SAE oil viscosity vs. Centipoise