Which is more ideal?

[buster]

http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic&f=3&t=002857

In this example, the Amsoil 5w-20 outperformed the over expensive S2k 0w30 in viscosity stability. However, as others have mentioned, their is more going on here.

The 0w30 being more shear stable, only will thicken in most cases. In this UOA it became almost a 50wt oil. The 5w-20, will shear but to offset that, thicken making it look like it stayed in grade. Which do you think is more ideal? Do you gain anything when an oil thickens? As Terry said before, some oils are designged to shear. It wouldn't surprise me if some of Royal Purple's oils shear by design. M1R could also be like that.

If your going for max HP, you'd rather have the oil shear down to offset oxidative thickening. If you know that your bearings can handle the low viscosity, its not an issue.

So with the above UOA, would you rather the oil just move up a grade, or shear/thicken and remain somewhat in grade?

 

[427Z06]

buster, what's the virgin specs on the S2k 0w-30?

 

[bruce381]

"As Terry said before, some oils are designged to shear."

I do not think motor oil in genearal are designed to shear since they will fall out of vis grade.

It is more likely blenders using a cheaper VII with a higher SSI (shear stability index)
lower being more stable than higher number.

More due to costs than anything and that they will barely stay in grade to pass API.

If they shear out of grade in use they do not care it passed the API tests.
bruce

 

[Mamala Bay]

I think the Amsoil S2K results as far as increasing the viscosity may result from cleaning of sludge from petro use. We have no history of the vehicle and what oil was used prior to when the S2K was used.

I've used Amsoil 5w30 and 10w30 since the engine was new(1,000 mile). At 50,000 miles I used the Amsoil S2k 0w30 which gave better MPG and resulting in gas savings. The oil itself payed itself in it's use. After the 2nd run...I've never felt a better ball bearing engine feel and the hotter the oil got..the better it performed!

Looking at the price of fuel...I think I am going to stick with the S2K after 100,000 miles on my engine. I run the S2K on a 3.0 Ranger which calls for a 5w-20...I see no issue in my application(12,000 mile per OCI yearly).

 

[peakperformance]

Based on my personal experience with AMSOIL S2K 0w30 I am of the opinion that there are other issues that cause it to thicken out of grade other than just extended use. I posted my most recent UOA a few weeks ago (http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=3;t=002809) and should have another one to post any day now. This vehicle was switched from the factory fill oil @ 3,750 miles to the S2K 0w30 and has been on it since. The only time it has thickened out of grade was the first change interval at 10,000 miles (6,250 miles on the oil). Ever since then it has been changed at ~10,000 mile intervals and has always been in the 12 cSt@100C range with a TBN of 6 to 9. Keep in mind this is a 2.0L Turbo putting out about 290hp, and is driven hard daily and taken to the track frequently. I see so posts on here of people switching from one oil to another and I can't help but think that it is not ideal to do so. Personally I believe that choosing a quality oil and sticking with it over the life of the vehicle will yield the best results.

 

[427Z06]

quote:

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Originally posted by Mamala Bay:
I think the Amsoil S2K results as far as increasing the viscosity may result from cleaning of sludge from petro use.

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Let me suggest you do a survey of the used oil analysis here. Many more times than not, this stuff thickens out of grade. And there's virtually no evidence that it cleans out any prior sludge from conventional oils. Lab tests point to it's volatility.

 

[buster]

S2k starts at 11.2 cSt @ 100C. It's a mostly PAO based oil. It does thicken and I believe it has very little to do with cleaning.

My question though was sometimes an oil, such as the UOA above, will shear and thicken, giving the result that it hasn't changed it's viscosity. The 5w-20 could have been shearing, but thickening at the same time, causing it to remain a 5w-20. Both are desired qualities, but would you chose that or the S2k not shearing , but going up a grade or two? S2k is extremely over priced.

 

[peakperformance]

quote:

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Originally posted by buster:
S2k starts at 11.2 cSt @ 100C. It's a mostly PAO based oil. It does thicken and I believe it has very little to do with cleaning.

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I don't think this is a totally accurate statement. Yes there are several UOA that show S2K thickens over time, but I personally have (3) 10,000 mile interval used oil analysis that show it stays in grade even when it is abused for the 10,000 mile duration. It is not uncommon for my oil temps (I have a gauge/sensor in the oil pan) to be held at 110C for periods of 30 to 45 minutes at a time.

All I am saying is that it is not fair to simply say that S2K always thickens because it doesn't. Therefore there must be some key factors that cause it to thicken that have not been pin-pointed yet.

 

[bulwnkl]

I'd rather have an oil stay in grade than go off-grade, whether up or down. By that I mean move the x% off of starting viscosity that the various labs consider "out of grade."

Having said that, I do not know whether the XL-series is simultaneously shearing and thickening (and the S2K is only thickening) or not. Regardless what's happening, examples like that make it pretty certain I'll never be using the S2K while the XL-series is available.

 

[buster]

Unlike Mobil and RL, which use the same chemistry/additive across the board, Amsoil uses quite a few from various suppliers. Whatever they did to the XL line, it's worked out well. Remember though, not all engines are tough on oil and that Ford is one of them. The S2k will thicken in most engines, not all.

 

[jason07-1zzfe]

quote:

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Originally posted by peakperformance:
...
All I am saying is that it is not fair to simply say that S2K always thickens because it doesn't. Therefore there must be some key factors that cause it to thicken that have not been pin-pointed yet.

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No one said it always does. It's not exactly a mystery. Just because one engine doesn't do it doesn't mean it's not a problem. I would not say it hasn't been pinpointed either.
Those Focus UOA are a perfect example.

 

[Bill]

buster,

I ran the Amsoil 0w30 twice for over 13,000 miles and the oil did not thicken, this oil gave me better mileage compared to the Amsoil 5w30,
but I do see the 0w30 thickening a lot more then I think it should in the used oil analysis on BITOG,
the 0w30 thickening with some of the short OCI's such as around 6,000 or 8,000 miles I think something else is at play here.

For preference of whether I like an oil to thicken or shear, as long as the oil did it's job and does not show excessive wear in analysis, does it matter?
Now for an oil thickening or shearing and leaving deposits (sludge, etc.) in the engine, which I do not want, I have not seen enough information that proves this.

 

[Geoff]

bruce381, do you have any experience with Shell's XHVI visc improvers? I hear they represent some of the better technology/quality but would like further opinions.