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Thought y'all'd like this. Note the shrinking differences between synth and dino oil, like comparing valvoline to mobile 1.


Happy Holidays!






These are the most comprehensive and recent ones I could find. They date to March 2003 and May 2003. I will post the numbers, add a comment or two, and answer any questions you may care to pose. These tests were commisioned by Amsoil, but since they use standardized ASTM protocols, they could easily be verified, and any deception challenged. Based on my experiences with the products from all these companies, and the results of similar but less comprehensive tests posted elsewhere, these do not look doctored or suspect. But as I did not oversee them, I cannot and will not be accountable for any discrepancies, real or imagined. This was a lot of work to type, and I strived to get them right.


1. All the oils were 10w30 viscosity

2. The oils tested were:

Amsoil (syn)

Castrol GTX Drive Hard (mineral)

Valvoline Synpower (syn)

Mobil Drive Clean (min) - isn't this the rebadged Honda oil?

Pennzoil Purebase (min)

Quaker State (Syn)

Quaker State Peak Perf (min)

Castrol Syntec (syn)

Valvoline (min)

Pennzoil Synthetic (syn)

Mobil1 SuperSyn (syn)


The following ASTM tests were run:

Thin-film Oxygen Uptake ( D-4742)

High Temp/High Shear ( D-4683)

NOACK Volatility ( D-5900)

Pout Point (D-97)

Total Base Number (D-2896)

Cold Cranking Simulator D-5293)

4-Ball Wear (D-4172)


Test 1: Thin Film Oxygen Uptake:

Measures the oxidation stability of an oil.

The induction time (break point) in minutes is measured. The test uses standard amounts of fuel dilution, soluble metals, and water to offer a real-world applicability.


Results for this test(all units in minutes):

Amsoil: >500 (no break)

Mobil1: 397

Pennzoil Purebase: 242

Castrol Syntec: 221

Valvoline: 219

Vavoline SynPower: 211

Mobil Drive Clean: 209

Quaker State Peak Performance: 192

Pennzoil Synthetic: 159

Quaker State Synthetic: 159

Castrol GTX Drive Hard: 132


Test 2: High Temperature/High Shear (HT/HS)

Measures a lube's performance under severe heat and shear (mechanical stress) as would be found in the journal bearings under heavy load. The units displayed are viscosity based, using the centipose unit (cP). The minimum spec for a 30w is 2.9 cP.


Results for this test (all units in cP):

Amsoil: 3.51

Quaker State Peak Performance: 3.37

Castrol GTX Drive Hard: 3.35

Vavoline SynPower: 3.30

Mobil1: 3.30

Valvoline: 3.30

Mobil Drive Clean: 3.28

Pennzoil Purebase: 3.16

Quaker State Synthetic: 3.15

Pennzoil Synthetic: 3.14

Castrol Syntec: 3.13


Test 3: NOACK Volatility.

Measures the evaporative loss of lubricants in high temperature conditions. The higher the number, the thicker the lubricant will become. API SL and GF-3 specs allow for a 15% evaporation limit. In this test, obviously, lower is better. Syns almost always have an advantage due to their monomolecularity.


Results for this test (% weight loss):

Amsoil: 4.86

Vavoline SynPower: 7.03

Castrol Syntec: 7.77

Quaker State Synthetic: 7.80

Pennzoil Synthetic: 8.15

Mobil1: 8.92

Castrol GTX Drive Hard: 8.93

Quaker State Peak Performance: 10.63

Mobil Drive Clean: 10.83

Pennzoil Purebase: 10.93

Valvoline: 12.18


Test 4: Pour Point

This test reveals the lowest temperature at which a lubricant will flow when cooled under test conditions. The lower, the better the product will perform in getting from the oil pan to the upper oil galleys, and in providing oil pressure quickly. Synoils generally are the best, because they are free of wax crystals, but today's mineral oils are better refined to remove wax impurities, and use advanced pour point depressant additives to help offset the synoils' intrinsically better properties.


Results for this test (all units in degrees Centigrade):

Amsoil: -48

Mobil1: -46

Vavoline SynPower: -46

Castrol Syntec: -43

Pennzoil Synthetic: -40

Quaker State Synthetic: -40

Pennzoil Purebase: -37

Valvoline: -37

Mobil Drive Clean: -37

Castrol GTX Drive Hard: -37

Quaker State Peak Performance: -34


Test 5: Total Base Number (TBN)

TBN displays the lubricant's reserve alkalinity, and is, of course, the opposite of TAN (total acid number). A high TBN will help resist the formation of acids from sulfur and other sources. It is also a good indicator of reserve resistance to oxidation. The higher the number, the superior ability to suspend contaminants and the greater the ability to provide long-drain intervals

Results for this test (all units in mg KOH/g):

Amsoil: 12.34

Vavoline SynPower: 11.38

Castrol Syntec: 10.39

Pennzoil Synthetic: 9.73

Mobil1: 8.57

Valvoline: 7.88

Quaker State Synthetic: 7.82

Castrol GTX Drive Hard: 7.74

Mobil Drive Clean: 7.71

Quaker State Peak Performance: 7.55

Pennzoil Purebase: 7.40


RR's comments: I was very impressed with all the oils, as the mineral oils have significantly improved, consistent with previous comments about how mineral oils are closing in, and that the GF-3 spec has resulted in very good performing products. Mobil1's showing is the best i have seen for that product, which usually was in the 5-6 range previously. It certainly also supports my previous comments that the 3K oil change "necessity" is out of place with current technology. Like an enema for a dead man, while it may not help to do a 3K change, it wouldn't hurt I guess.


Test 6: Cold Crank Sumulator

This one determines the apparent viscosity of the oils at low temperatures and high shear rates, simulating the dreaded cold start. It has direct applicability to engine cranking, the lower the number the better in terms of stress on the battery, starter, etc. A 10w is tested at -25degF and must show a vis <7000 cP to pass.


Results for this test (all units cP at -25degC):

Pennzoil Synthetic: 3538

Amsoil: 3590

Mobil1: 3967

Quaker State Synthetic: 4142

Vavoline SynPower: 4541

Quaker State Peak Performance: 4620

Castrol Syntec: 4783

Castrol GTX Drive Hard: 5804

Pennzoil Purebase: 5936

Mobil Drive Clean: 6448

Valvoline: 6458


RR Comments: If you live and drive your car in very cold climates, the advantage of the synoils is obvious. Keep in mind that the NOACK performance figures here as well, as this tests hows the performance of fresh oil - after a few thousand miles, the oils with higher volatility will likely have thickened, unless there has been high dilution from fuel, such as can occur if excessive startup idling warmups are employed.



Test 7: Four Ball Wear

This one is a good indicator of the wear protection of a lubricant, although in the real-world it is should be factored in with the TBN of the oil. Three metal balls are clamped together, and a rotating 4th one is pressed against them in sliding contact. A scar is produced, since at some point the film strength (resistance to being squeezed out) of the oil will be exceeded. The scar is then measured, and the smaller the average wear scar, the better. This test is affected by both the base stock of the oil, and its additive package.


Results for this test (all units in inches):

Amsoil: 0.40

Castrol Syntec: 0.45

Vavoline SynPower: 0.55

Quaker State Synthetic: 0.55

Mobil Drive Clean: 0.55

Pennzoil Synthetic: 0.60

Mobil1: 0.60

Valvoline: 0.60

Castrol GTX Drive Hard: 0.60

Quaker State Peak Performance: 0.60

Pennzoil Purebase: 0.65



RR Comments: Amsoil and Castrol Syntec are the clear frontrunners, indicating excellent chemistry and use of anti-wear additives. Once again, the high performance of the mineral oils against the 2nd tier synoils is notable, although one cannot dismiss the superiroity of the synoils across the board.




Final comments:

I think that except for one of the lubes, there was a wide discrepancy of performance for the others - one might be good here, not so good there. As in life, consistency of performance is what sets apart the great from the good.

As Voltaire said, "The best is the enemy of the good". Perfectly good performance can be found in any of these products, and a thinking owner would factor his/her driving styles, operating conditions (environmental), maintenance schedule (intervals between changes), cost constraints, buy vs lease, and expected length of ownership into making a choice.


Now, what about the other top synoils? Well, they were not tested here, but certainly the industry giants were. Based on tests I have run or seen from sources I trust in the industry, Red Line, NEO, Motul, and others would likely score in the top quartile of these tests. The tests anmd UOA's I have seen for Royal Purple have never shown it to be other than mid-tier, competitive with the synoil or GIII mineral oils from the major companies.


Hope this is useful to you - I found it fascinating to watch the goo go head to head.


Happy Motoring!!

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I think Amsoil aimed at the top selling competitors when they commisioned this test. I would like to think they didn't leave out any competitors that would have beat them, but maybe they did. I kind of enjoy seeing Mobil 1 put in it's place where I think it belongs based on my experience with it.

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I would first question the TBN of Mobile1. In the neptune spacebears extended oil change test Blackstone Labs gives Mobile1 a 11.8 compared to 12.5 for Amsoil. I don't doubt that Amsoil is an excellent product but have trouble with any test they conduct. I know people that use Amsoil and swear by it. The hydrocracked oils are becoming great products that are closing the gap between "true" synthetics. In business college I was taught to question the goal or objective of any test or research as to what the desired end results would be. For Amsoil it will always be to come out on top because they are running the test. Glenn Taylor.

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There are similar grumblings on other boards regarding amsoil's test setup. OTOH, not an amsoil user, I found the comparisons with the other oils better than the typical, "I use X and I like it because...." claims. Went ahead and put valvoline in the miata after reading this (not enough of a mileage car for synth in our case).



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Mike, Me neither because you just can't walk into any store and purchase it. Also they love to kick Mobile around alot. I have used synthetic on most all our vehicles since 1978 without any issues at 10k changes when the warrenty ran out. Glenn Taylor

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UOA's are the only real way to see how an oil performs in any particular engine or application. testa above show some useful info but you must read between the lines. M1 SS, Pennzoil Purebase etc show excellent UOA's and BITOG has a good UOA section. Search there for oil type or engine to see what performs best in yours.

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This is the one they use to really jump ahead on, yet I don't see the relevance to an engine that uses plain bearings. These have sufficient surface area not to challenge the oil film-strength. Even camshaft lobes excert force over a line, not a point.


This test is misleading.

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This is the kind of high-class stuff that sets this group apart from the rest of the motoring public if not the public in general: A well written bit of information that took time and effort to post AND some serious challenging rebuttal and disagreement in a totally agreeable professional manner.

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this test may show amsoil in the lead, but imo i don't much care for amsoil.. my acura had amsoil in it its entire life, and when i had to do a headgasket i inspected the cams and runners .. cams and runners were both scored and grooved more than i've seen with any other oil.. i just wasn't impressed with payin that much for the oil and having a torn up engine..


on the other hand my turbo wagon has had castrol dino oil run in it its entire life and its still kickin with 290k original... going to tear it down at some point and see how well it fared.. my guess is alot better than the acura with amsoil...

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Amsoil doesn't need me to defend it, but I must add, virtually any modern oil and filter changed at the proper interval will prevent the kind of damage you describe, so it's likely that something else was the problem. It's impossible to be conclusive with a sample size of 1.


Using any oil for extended drain intervals requires periodic analysis to determine the oil's suitability for continued use. I think that Amsoil misleads consumers by claiming that their oils can be used for 25k miles without insisting on periodic analysis. Some of the more reputable dealers may be trustworthy, but the company as a whole leaves a bad taste in my mouth. I do really like the 5w-30 ASL and 10w-30 ATM products though.

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Meep, very interesting study with very surprising results. I'm mostly tinking of their finding that most metal wear occurs during the first 3,000 miles and that it gets lots lower after that. Conclusion: relatively old oil protects your engine more than fresh oil!!!

And they see a change interval of 8,000 miles with Mobil 1. That's almost 13,000 kilometers!

Like learning that cigarette smoke is good for your lungs!


I hope someone will some day test oil in an environnement like the one I drive in for most of the year: cold weather, short distances, stop and go, etc.

I actually change my oil every 3,000 miles or every three months whichever comes first (Mobil 1). But I might go a little longer than that after reading the results of their tests.

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Frag try the Kublin method that is also on their site to see what numbers you get. With Mobile 1 your figures will exceed 7.5k changes I am willing to bet. Glenn Taylor.

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