Which oils are 'thick or thin' ?

[Seth]

Very well said ... There is more to oil than just Centistokes and HTHS... such as low Noack volatility, high TBN, low pour point and low wear scar to name some. I understand that some specs on PDS can be misread if you are not well informed. For example sulfated ash has to be taken into consideration with ZDDP etc if I am not wrong. Even then, reading PDS can be tricky.. For example Amsoil 0W20 reads a wear scar of 3.5 diameter which puts it in the league of amsoil 0w30. But upon closer inspection, you can see that test was ASTM D-4172B was done for 0w20 and ASTM D-4172 was performed on 0w30. Difference is that 0w30 gave the same wear scar at double the temps and higher RPM. Now, keep in mind that 5w30 and 10w30 didnt do any better than 0w20 in this regard. This is surprising because you'd expect 10w30 to do better than 0w30 in wear test. Reason could be that higher the spread, more PAO goes into base stock. This is all my conjecture at this point but thinner the spread, then perhaps adding heavy viscosity modifiers and pourpoint depressants can do the trick and relatively less PAO is needed. But props go to 10w30 in the Noack department as it beats out easily all the thinner oils of its breed. Here are the specs from amsoil site:

http://www.amsoil.com/storefront/asm.aspx
http://www.amsoil.com/storefront/tso.aspx
http://www.amsoil.com/storefront/asl.aspx
http://www.amsoil.com/storefront/atm.aspx

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Base on those fact, which one is more important? Visc @100degC or HTHS number? Or maybe other point? Thanks for reply..

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With these three data points I don't know if it is as simple as which is most important.

In some ways, I wish I had added cold cranking, NOACK Volatility, and Viscosity Index as well. And even then there is far more to picking the right oil.

I think our chart just allows some quick reasearch as to whether a given oil is thinner than, typical of, or thicker than other oils in the same grade.

This might allow us to pick an 'thinner' oil for better mileage, or a 'thicker' oil for more protection in a modified engine or service use application, or to reduce oil consumption slightly.

The HTHS number should also be some help in determining if an oil will be better in a modified engine or service use application. Or, whether an oil might meet or exceed one aspect of a factory approval.

I drive hard, so I still think that a thicker oil at 100 C and a higher HTHS number means improved protection.

If I did lots of cold starts, and drove easy...then I might think that cold cranking was most important.

Other forum members might weigh in with their insights, and reveal what I have overlooked or mistated.

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[tsmay51]

Maybe I don't get it.... How can certain oils be thick or thin within the same rating? I guess what I am asking is 2 oils are rated at say 5W-20 would they not be very close to one another? I know they could vary some but would it not be verry little? Please educate me on this.

 

[jmac]

You got to remember, you are dealing with a group of people here who differentiate between a 9.5 cSt 30 wt @ 100c and an 11.5 cSt 30 wt @ 100c. Not everyday people.

 

[Thatwouldbegreat]

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Maybe I don't get it.... How can certain oils be thick or thin within the same rating? I guess what I am asking is 2 oils are rated at say 5W-20 would they not be very close to one another? I know they could vary some but would it not be verry little? Please educate me on this.

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If you look at the chart you'll see that oils are on a spectrum from thin to thick. But we don't buy oils that are labeled 5W-22, 5w-25, 5W-29, 5W-32, 5W-39 etc.

Any oil that is within the lower or upper limit of a 5W-30 is labeled 5W-30 ....yet some are very close to a 5W-20 and some are close to a 5W-40.

Many of the 'High Mileage' oils are near the upper range for thickness for the grade. Sometimes running a 5W-30 that is close to a 40 weight can reduce oil consumption.

Just as a 5W-30 that is closer to a 20 weight might give better gas mileage or cold weather start up.

I think this data is also helpful while in warranty, since the manufacturer specifies a certain weight oil. It is much easier to run a 5W-30 if that is what is specified in the owner's manual than explain to the Service Manager that you chose a 5W-20 or 5W-40.

Knowing which oil is 'thick or thin' allows the owner to pick an oil better suited to hot or cold weather... or for heavy duty driving, or for improved gas mileage.

In our Subaru Outbacks the owner's manual oil chart specs 5W-30 but clearly specifies heavier oils as temperature or work load increase.

In my case with extreme cold , extreme heat, and demanding mountain driving I like a wide range 0W-30 synthetic oil which is really close to a 40 weight oil yet is also a good choice for cold starts in sub zero.

This comes in very handy when an oil change in sub zero January might not be due for a change until after 100 degree + August.

Running 7000 mile oil changes that are good for all conditions from 12,000 feet above sea level in 30 below to Las Vegas and 114 degrees,is so much better than the old 3000 mile oil changes using oil that should also be changed to better match season or location.

Also when looking at oils like Redline Polyol Ester synthetic which behaves dynamically like a much thicker conventional grade these charts help to identify that Redline 5W-30 might be a good choice when with a different oil a 5W-40 or 10W-40 would have been the best choice.

I'm probably beating a dead horse here, but our 1995 BMW 325ic specs a thicker oil like a 5W-40, but using the data on individual oils as well as factory approvals I was able to feel comfortable running yet again a very high quality and unique 0W-30 synthetic , Castrol Syntec 0W-30 that was made in Germany. [ the now hard to find 'Green GC' ]

 

[Carmudgeon]

Pennzoil has finally provided specs for their PP 15W-50:

143 cSt @ 40°C
21.4 cSt @ 100°C
5.1 HTHS
175 VI

 

[crw]

Please excuse the newbie question here, but why are we concerned about the 40 degrees C datapoint? 40 C is around 104 F... Why not a COLD datapoint like -40C? I realize that this is probably what the industry standard is for publishing the numbers, but is this telling us anything about "cold"?

Just need to balance out my choices based on the -20F cold mornings that will be here in a few months....

 

[Rockstock]

Found http://www3.shell.no/op/smidler/prodhbok/helixult.htm with references to Shell Helix Ultra Specs (HTHS). reproduced here partially.

Viskositetsgrad, SAE 0W-40 5W-40 10W-60
Viskositet, cSt/40°C 75,2 74,4 151
Viskositet, cSt/100°C 13,6 13,1 22,8
Viskositetsindeks 187 187 0,85
Flammepunkt, °C (COC) 215 215 215
Flytepunkt, °C -42 -39 -39
Densitet, kg/l v/15°C 0,840 0,840 0,851
HTHS viskositet, cP/150°C 3,68 3,68 5,42

 

[LoneRanger]

(Note: Above is from May 2007)