Should they rename Oil Grades?

[BritGerCarLuvr]

After reading Oil 101 posted by Bob, I now realize that I might have been believing certain myhts as being "true". I've been very confused, even obsessed about certifications and grades in my choice of oils - right up unitil now. If I learned right, all that really matters is the 40C Viscosity & the 100C Viscosity. That's where the answer lies. Therefore I've compiled this small bit of info, and if you follow my thoughts, perhaps one of you folks can agree (or) disagree with my logic.

Mobil 1 Advanced Fuel Economy 0W30, 40C=56.7, 100C=10.6, VI=180, HTHS=3.06
Mobil 1 EF 0W40, 40C=75.0, 100C=13.5, VI=185, HTHS=3.80
Castrol GC 0W30, 40C=72.0, 100C=12.2, VI=167, HTHS=2.90
Tot Qrtz E 0W30, 40c=68.4, 100c=12.2, VI=170, HTHS=>3.5
Pennzoil Ultra 5W30, 40c=57.5, 100c=10.3, VI=169, HTHS=3.10
Castrol EDGE 5W30, 40C=54.1, 100c=9.80, VI=???, HTHS=????

1) Since the "Ideal" viscosity for an engine at temp is a 10.0, and the LOWER the viscosity at 40C, means a less "thick" oil, strictly based on these facts, Mobil 1 Advanced Fuel Economy 0W30 or Pennzoil Ultra 5W30 will provide practically identical cold startup performance, and protection at running temp. Edge 5W30, will "flow" a bit more cold, but might not "protect" as well at running temps.

2) Why don't they simply label oils based on their Cold/Hot performance? For example, instead of Mobil 1 Advanced Fuel Economy 0W30, Why not Mobil 1 Advanced Fuel Economy 57/11 (57 being the COLD perf, and 11 the HOT (rounded))?

3) From what I see, the "perfect" COLD start properties/HOT protection choices will be the Mobil 1 Advanced Fuel Economy 0W30 and ironically the Pennzoil Ultra 5W30 with a very close third going to Castrol Edge 5W30. It is very strange to me that the 0W30 specs are almost identical to the 5W30 specs in these cases. Of course, again that is in keeping with the "ideal" 10 at running temperature.

So I ask... where does the VI 167>185 come in? Which is better? It seems from some of the answers I have had that the higher the better, yet Mobil 1 0W40 has an astronomical 75 Cold start fluidity and is still a "0" weight, at least supposedly.

As far as HTHS goes, the higher the better it seems, but since I religiously change my oils every 5000 miles (8000 KMS), evidently, oils shreading, thinning, falling apart, is NOT an issue. I sure hope I got that right.

Therefore, based on Oil 101, The ideal oil would be the Mobil 1 Advanced Fuel Economy 0W30, with a relatively high VI, Low cold number, a higher 10.6 hot number for all the vehicles.

Now, I can't help myself but to return to the magic question, or puzzle. The oils that meet the BMW-LL and B 229.5 all have a 12-13 hot and a much higher 68-75 cold number. I went from a 75 cold to a 68 cold, and there was a DRAMATIC difference (the BMW)- just imagine a 54? but the low cold number oils do not meet the LL/229.5 yet they advertise 15,000 miles between oil changes just as the LL oils do.

Maybe I am missing something somewhere with the VI?
Am I getting this, or am I heading totally in the wrong direction?

I truly appreciate all the insight/replies I have had from a lot of you folks. I spent a lot of money on my cars, and I really hope to keep them a long time. The BMW and the Benz are NOT on Warranty, the Jags are, Both till 2014, BUT, the Supercharged will probably mileage out in the next year and a half or so. The X only has 40K miles on it.
Once agin, Thank you.

 

[Audi Junkie]

Meh, I just use the published viscs and visc calculator to compare oils at 0f, the realistically coldest I will see. I have Castrol EDGE 5w30 in for winter, obvious reasons.

http://widman.biz/English/Calculators/Graph.html

 

[m37charlie]

Originally Posted By: BritGerCarLuvr
am I heading totally in the wrong direction?



You are headed in the wrong direction.
Use oil that meets the mfgs. specification. Period.
For example, BMW/Mercedes want oils that have HTHS>3.5, which is well-nigh impossible with a vis of 9.5-10@100C.
Mobil 1 0W40's 40C. vis of 75 is not "astronomical". The fact that it increases by a factor of less than 6 from 13.5@100C. give it its' very high VI and when graphed

http://www.widman.biz/English/Calculators/Graph.html

has a nice viscosity at -35C., meeting the 0W spec.
Don't make specific conclusions from (flawed) general discussions.
Buy the oil that you like from the mfgs list, for example:
http://bevo.mercedes-benz.com/bevolisten...ent_action=show

Charlie

PS: If you want a recommendation for all your vehicles, use Mobil 1 0W40

 

[A_Harman]

You are reasoning on the assumption that 40C viscosity values are related to cold flow properties. This is not true. Since 40C=104F, that is more like the temperature that your oil would be when restarting your engine in Texas on a hot day. If you want to understand cold flow properties of oil, look at the Cold Cranking Simulator or Pumpability viscosities. It is these values that set the xW number on the oil bottle. The lower the w-number, the lower the allowable viscosity to get a given rating. The lower viscosity that an oil has, the quicker it can be pumped to the farthest reaches of your oil system on a cold day.

I don't get too hung up on Viscosity Index, because it is a direct mathematical function of the KV40 and KV100 numbers. Play with the Widman viscosity calculator that Audi_Junkie linked in his message.

The number I look at if I am going to be operating an engine in hot conditions under heavy load is HTHS. This gives an indication of the protective ability of an oil when it is being sheared between moving surfaces at 150C. The higher the number, the thicker the oil film. The problem with oils that have been loaded with large amounts of VI Improver to get a wide range of viscosity, is that they lose viscosity when placed under shear. So an oil that meets the KV100 number for a 40-weight may only have an HTHS number for a 30-weight.

As an example from your list:
Pennzoil Ultra 5w30: KV100=10.3, HTHS=3.10
And one of my favorites:
Redline 5w30: KV100=10.6, HTHS=3.80

Only a 3% difference in kinematic viscosity, but a 25% difference in high-temperature, high-shear viscosity. Which do you think would protect better in your engine?

 

[A_Harman]

Originally Posted By: BritGerCarLuvr
As far as HTHS goes, the higher the better it seems, but since I religiously change my oils every 5000 miles (8000 KMS), evidently, oils shreading, thinning, falling apart, is NOT an issue. I sure hope I got that right.



There are two aspects to oil viscosity loss due to shear. One is the temporary loss that occurs as the oil passes between moving surfaces. The other is permanent loss that occurs over time as the oil is continuously recirculated through the engine. High amounts of VI Improver makes an oil more susceptible to both of these phenomena. Even if you are changing your oil every 5000 miles, it does not protect from the temporary viscosity loss due to shear: this occurs whenever the oil is in a bearing under motion. By changing your oil every 5000 miles, you are protecting against permanent viscosity loss (shearing down in grade).

 

[Quattro Pete]

Originally Posted By: BritGerCarLuvr

So I ask... where does the VI 167>185 come in? Which is better? It seems from some of the answers I have had that the higher the better, yet Mobil 1 0W40 has an astronomical 75 Cold start fluidity and is still a "0" weight, at least supposedly.
, VI is just a calculated value based on the two Viscosities (at 40C and at 100C). The larger the difference between the two, the higher the VI value will be. There are online calculators out there that will spit out the VI value when you plug in the two viscosity numbers.

Quote:

As far as HTHS goes, the higher the better it seems, but since I religiously change my oils every 5000 miles (8000 KMS), evidently, oils shreading, thinning, falling apart, is NOT an issue. I sure hope I got that right.

Higher HT/HS is not better if your engine does not require it. If it does not require it, all you're doing is robbing it of MPG by running high HT/HS oil in it.

On the other hand, if your engine requires it, then it requires it regardless of how often you change oil, every 10 miles or every 10,000 miles.

 

[NateDN10]

I do sometimes wish that they would provide viscosity at, say, 0C instead of 40C.

For example, according to Widman's calculator, Castrol Edge 5w30 has an almost identical viscosity to Mobil 1 0w30 at 0C, despite the different cold rating. And Castrol Syntec 5W-20 is significantly higher!

 

[A_Harman]

Originally Posted By: NateDN10
I do sometimes wish that they would provide viscosity at, say, 0C instead of 40C.

For example, according to Widman's calculator, Castrol Edge 5w30 has an almost identical viscosity to Mobil 1 0w30 at 0C, despite the different cold rating. And Castrol Syntec 5W-20 is significantly higher!


I agree. 40C is a temperature that the oil passes through so quickly during warmup that it doesn't really have the same consequence of operation at the stabilized high temperature of 100C, or the critical transient for starting at 0C.

But since we can all use the Widman calculator, we can figure that stuff out for ourselves.

 

[Quattro Pete]

Originally Posted By: BritGerCarLuvr

1) Since the "Ideal" viscosity for an engine at temp is a 10.0,

Is it really ideal for every engine?

 

[CATERHAM]

Originally Posted By: Quattro Pete

Quote:

As far as HTHS goes, the higher the better it seems, but since I religiously change my oils every 5000 miles (8000 KMS), evidently, oils shreading, thinning, falling apart, is NOT an issue. I sure hope I got that right.

Higher HT/HS is not better if your engine does not require it. If it does not require it, all you're doing is robbing it of MPG by running high HT/HS oil in it.

HTHS viscosity is best thought of as a very accurate viscosity measurement that closely replicates an oil's viscosity acting under pressure in a IC engine.
That's why fuel economy and even an engine's oil pressure correlates with HTHS vis as opposed to the KV100 spec'.
The following post explains in further detail:

https://bobistheoilguy.com/forums/threads/hths-vis-spec-trumps-the-kinematic-100c-vis-spec.137739/

 

[CATERHAM]

Originally Posted By: Quattro Pete
Originally Posted By: BritGerCarLuvr

1) Since the "Ideal" viscosity for an engine at temp is a 10.0,

Is it really ideal for every engine?

Agreed. 10 what?

Ali Haas, who wrote Oil 101, over simplified just to illustrate the point that all motor oil, regardless of the grade is too thick until you get some heat into it to thin it out to something like the kinematic viscosity of 10cSt. Since kinematic viscosity is not an accurate measure for an engine (doesn't take pressure into consideration), using the more precise HTHS methodology to gauge a viscosity of 3.5cP to 4.0cP might be close to the optimum for most modern engines.

 

[dparm]

Originally Posted By: NateDN10
I do sometimes wish that they would provide viscosity at, say, 0C instead of 40C.

For example, according to Widman's calculator, Castrol Edge 5w30 has an almost identical viscosity to Mobil 1 0w30 at 0C, despite the different cold rating. And Castrol Syntec 5W-20 is significantly higher!


We've learned that at low temps, we're more interested in how easy the oil is to pump...kinematic viscosity isn't as useful down low.