Rethink and understand SAE viscosity: a 0W-20 can be thicker than a 0W-40 or 5W-40

[camrydriver111]

How did you calculate the HTFS values?

 

[Astro14]

How did you calculate the HTFS values?

Extrapolation. Based on some known measurements of some oils.

Note that the extrapolation assumes all base stocks, and all additives, have the same viscosity changes with temperature.

This is a specious assumption that throws the entire HTFS calculation into the realm of spreadsheet amusement.

 

[benjy]

a geat long read i will finish later + as always LOVE the factual info on machinery lubrication + that they DISTINGUISH between mineral synthetics + the REAL stuff as well as the better + lesser characteristics! would love to find the graph machinery lubrication showed as to how much more mineral oils thinned with heat + especially the thickening even more so in cold!!! brother in law noted as he added a 5-20 wolfs head oil stored in his truck at temps in the 20's + less was SOOOO thick!! it came from the used "car" lot he usually buys from that sells REALLY used vehicles for lower prices. good for a thrifty person that like me drives little + is RETIRED!!!