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

How did you calculate the HTFS values?

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.

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!!!

This is my conclusion about the SAE J300 viscosity specification: It is obsolete and does not give the full picture.

SAE J300 was updated in the mid-1990s to correct inherent problems associated with it by introducing the HTHS viscosity, which is measure at 150 ℃ and a shear rate of 10⁶ s⁻¹. At that time, viscosity meters were limited to a shear rate of 10⁶ s⁻¹. However, the HTHS viscosity does not directly relate to engine wear.

Recently viscometers capable of measuring at shear rates of 10⁷ s⁻¹ have become possible. I introduced the HTFS viscosity, which is measured at a shear rate of 10⁷ s⁻¹ or higher (as shear rate → ∞).

The HTFS viscosity will determine the wear protection of an oil—higher HTFS for more wear protection. HTFS and viscosity index (VI) will determine the fuel economy—lower HTFS and higher VI for better fuel economy.

If my table is sorted by HTFS, you will see that some 0W-20 oils are thicker than some 0W-40 oils. For example, Ravenol ECS 0W-20 is thicker than M1 FS 0W-40. Therefore, before you get into any "thick vs. thin" debate, understand that the SAE viscosity grade does not paint the whole picture and a 0W-20 can actually be very thick.

HTFS and VII-content table sorted in decreasing HTFS

This is my conclusion about the SAE J300 viscosity specification: It is obsolete and does not give the full picture.

SAE J300 was updated in the mid-1990s to correct inherent problems associated with it by introducing the HTHS viscosity, which is measure at 150 ℃ and a shear rate of 10⁶ s⁻¹. At that time, viscosity meters were limited to a shear rate of 10⁶ s⁻¹. However, the HTHS viscosity does not directly relate to engine wear.

Recently viscometers capable of measuring at shear rates of 10⁷ s⁻¹ have become possible. I introduced the HTFS viscosity, which is measured at a shear rate of 10⁷ s⁻¹ or higher (as shear rate → ∞).

The HTFS viscosity will determine the wear protection of an oil—higher HTFS for more wear protection. HTFS and viscosity index (VI) will determine the fuel economy—lower HTFS and higher VI for better fuel economy.

If my table is sorted by HTFS, you will see that some 0W-20 oils are thicker than some 0W-40 oils. For example, Ravenol ECS 0W-20 is thicker than M1 FS 0W-40. Therefore, before you get into any "thick vs. thin" debate, understand that the SAE viscosity grade does not paint the whole picture and a 0W-20 can actually be very thick.

HTFS and VII-content table sorted in decreasing HTFS

Nice chart. Any chance you could include some mid-SAPS options in 5W-40, 0W-40? Or is mid-SAPS really not worth worrying about outside Europe? (Even OEMs don't seem to bother)

Nice chart. Any chance you could include some mid-SAPS options in 5W-40, 0W-40? Or is mid-SAPS really not worth worrying about outside Europe? (Even OEMs don't seem to bother)
OP has been MIA since 12/21/22. Doubt he’s gonna answer.

What's with that Toyota TGMO 0W-20 SN in your table (ranking oils from highest HTFS to lowest) that's 2nd from the bottom with a HTFS of only 1.55 cP?
When you make your engine to sub-nanometer tolerances from nearly indestructible materials and extremely efficient designs, it turns out, you don't care as much about oil having to save your engine from itself? My brother drove our 1985 Tercel some 1,000 miles with no oil before it finally burned up. Something about converted airplane factories that were originally to make planes that could get you home from halfway across the Pacific after taking heavy enemy fire.

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When you make your engine to sub-nanometer tolerances from nearly indestructible materials and extremely efficient designs, it turns out, you don't care as much about oil having to save your engine from itself? My brother drove our 1985 Tercel some 1,000 miles with no oil before it finally burned up. Something about converted airplane factories that were originally to make planes that could get you home from halfway across the Pacific after taking heavy enemy fire.
What? That makes no sense.

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