This is a long list of oil wear protection and zinc content from a corvette site. I know its long but I think it's worth looking at.
I think folks would generally agree that the most important thing a motor oil does, is prevent metal to metal contact. Everything else it does comes after that. Liquid oil is incompressible, no matter what the viscosity. So, in the places and conditions inside an engine where you have enough flow between parts to maintain a presence of liquid oil without it being squeezed away, all oils will offer similar protection in preventing metal to metal contact.
But, under extreme loading and/or heating conditions, as well as at flat tappet interfaces, distributor gear interfaces (particularly those with high volume oil pumps), BBC lifter bore primary thrust surfaces (due to tilted pushrods and often offset pushrod seats in the lifters, along with high spring pressures), and cold start-up where oil has run off, to name just a few examples, you can be left with only a very thin “film of oil” to prevent metal to metal contact, rather than enough flow to have a presence of liquid oil.
In these cases, an oil’s “load carrying capacity/film strength” is all-important to prevent wear. And in this regard, oils vary greatly. But finding this data for comparison is nearly impossible because most oil companies do not publish this type of info. And when you can on occasion, come up with some data, you never know if you can trust its accuracy because it will typically be advertising based.
I consider “load carrying capacity/film strength” to be the first thing to consider when choosing a motor oil to run. Detergent/dispersant levels for anti-deposit buildup/anti-sludge, TBN acid neutralizer levels, anti-foaming agent levels, and NOACK volatility percentages, etc, etc, all come after that.
So, I bought an oil “load carrying capacity/film strength” tester. This gives me the capability to test and compare various oils head to head, using the exact same test equipment and the exact same test procedure. That way I’d know the truth first hand. The testing was performed in Southern California during February and March 2012.
As far as I know, I’m the only one who has ever done such a wide ranging motor oil wear test. I went to all this trouble because I wanted to “KNOW” how good various oils are, rather than have to essentially guess. I really only did this testing for my own knowledge, and to share it with a handful of car buddies. But a few of those car buddies talked me into posting the info on some of the Forums, so that everyone could get a chance to see all the data. So, the test results are shown below, for those who might like to see them.
I’ll make it perfectly clear right up front. My testing was not done inside a running engine. I tested 44 different oils, and testing that many oils in a running engine was simply not practical, not to mention that there would be too many variables to have a true apples to apples comparison. All my testing was done with the oil tester. So, for those who put no value on data gathered from “Lab” testing, feel free to close out now, and go on to the next topic. For everyone else, read on.
My tester spins a test ring bathed in oil at 456 rpm (7.6 rev/sec), and a test specimen is “gently” brought down into contact with the spinning ring. A load is then “gently” applied to the test specimen and is “gradually” increased, so as not to suddenly punch through the oil film, and also to allow the zinc a bit of time to get hot and become effective.
At the conclusion of each 30 second test, the wear scar that is generated, is carefully measured with the aid of a magnifying glass to maximize accuracy. Then the psi that the oil supported, is calculated, which gives the value of its “load carrying capacity/film strength”. All the oils are of course subjected to the exact same test procedure, so they all have the same opportunity to perform as well as they can.
NOTE: The test results are intended to enlighten and inform, not to offend. And they were generated without bias towards any particular brand or viscosity. To prove that there was no bias here, my long time “oil of choice” Royal Purple, did not show up all that well. And I did not hesitate to show that. For better or worse, the numbers simply are what they are, and speak for themselves.
I have a copy of the official ASTM D 2782, the Standard Test Method for Measurement of Extreme-Pressure Properties of Lubricating Fluids (Timken Method). And for the record, ASTM D 2509, is the Standard Test Method for Measurement of Load-Carrying Capacity of Lubricating Grease (Timken Method). They are NOT the same test spec.
The ASTM D 2782 calls for testing the oil at 100*F, yes 100*F, NOT 100*C. Testing at that temperature is completely worthless in my mind. Because that is really just a hot “room temperature”, and is not hot enough to be representative of actual oil temperatures inside a running engine. And for example, 0W30 and 10W30 are not even the same viscosity at room temperature, but they are rated the same viscosity by the time they reach 212*F (100*C). So, in order to obtain the most valid data possible, I did all the oil tests at 230*F, which has all the same hot category multi-viscosity oils at the “same” viscosity, and is representative of oil temps inside a running engine. That being the case, I did not precisely follow what I consider the useless ASTM D 2782 standard.
Note:
*** The test procedure I used was developed and refined to obtain the best possible repeatability, which ensures the most accurate test results possible. Once I made the final revision to optimize the procedure, testing began and the exact same test procedure has been used over and over again for all the following tests.
*** I used 5W30 Castrol GTX conventional oil during the entire test procedure development phase, in order to keep things consistent. During that time, I tested it both HOT (230*F) and COLD (mid 60’s F). And it’s COLD “Load carrying capacity/Film strength” was about “TWICE” as high as its HOT capability. So, the hotter and thinner the oil, the lower its “Load carrying capacity/Film strength”.
*** The testing here only evaluates “Load carrying capacity/Film strength”, but does NOT test an oil’s slipperiness/friction reducing qualities. Load carrying capacity and slipperiness do NOT necessarily go hand in hand. For example, if we were to fill our engines with thick old school STP Oil Treatment, we’d have much higher “load carrying capacity/film strength”, but the HP would plummet due to all the extra viscous drag. Therefore, the testing here does NOT provide any information regarding HP increasing capabilities. But in the future, I do plan on doing a separate oil test on the “slipperiness/friction reducing qualities” of each of the oils tested below. So, stay tuned for that.
*** I was able to directly compare 20 wt type oils, 30 wt type oils, 40 wt type oils and 50 wt type oils because even at 230*F, all the oils stayed on the spinning test ring nicely without flinging off. Therefore, no viscosity had any advantage over another.
A few overview highlights of the results:
*** The High Performance and Racing oils did NOT dominate all the top ranking positions as expected. In fact, contrary to popular belief in the Hotrod and Racing world, simply having high levels of zinc/phos was absolutely NOT a guarantee of high “load carrying capacity/film strength”. Some high zinc/phos oils had excellent test results, while other high zinc/phos oils had only fair test results.
*** This testing has clearly shown that a particular oil’s “load carrying capacity/film strength”, is NOT determined just by its zinc/phos levels, but rather, it is determined by the oil and its additive package “as a whole”. So, if people choose an oil strictly based on its zinc/phos levels, they could easily end up having a “LOT LESS” protection than they think they have.
*** This testing has clearly shown that an oil’s viscosity is also absolutely NOT an indicator of its “load carrying capacity/film strength”. Among the 44 oils tested here, 50 wt type oils ranked from 6th to 40th, 30 wt type oils ranked from 1st to 44th, and 20 wt type oils ranked from 10th to 35st. So again, an oil’s “load carrying capacity/film strength” is determined by the oil and its additive package “as a whole”, nothing else.
*** This testing has clearly shown that you simply CANNOT PREDICT an oil’s “load carrying capacity/film strength” by looking at its specs or its viscosity. You can only determine that capability by performing some type of actual wear testing, as I’ve done here. But, there are of course other wear test methods that can be used as well, such as the 4 Ball Wear Test which is somewhat popular in the oil industry. Though I have only seen Amsoil list results from that type of wear testing. My tester and the 4 Ball wear tester are in no way attempting to duplicate engine internals. Instead, they are designed to test oils directly against each other in a controlled and repeatable manner.
*** The latest “LOW” zinc/phos API certified oils, both synthetic and conventional, performed WAY better than expected. In fact, they are so good that their capability has surpassed most of the traditional high zinc/phos High Performance and Racing oils.
*** “Low cost” conventional API certified oils performed WAY better than expected.
*** Lucas and Valvoline Racing oils performed very well.
*** Royal Purple High Performance, Racing and street oils generally performed below expectations.
*** Brad Penn High Performance and Racing oils performed below expectations.
*** With that said, there are no BAD oils here. Some are simply better than others in terms of “load carrying capacity/film strength”. Those that have a higher capacity, offer a higher margin of safety than those with a lower capacity.
Motor Oil Wear Test Results and Ranking
*** The higher the psi result, the higher the “Load carrying capacity/Film strength”, and the better the oil is at preventing wear.
*** All oils were tested at 230* F (representative of actual running temperature).
*** Multiple tests were performed on each oil, and those results were averaged to arrive at each oil’s final value shown below. Differences between oils of 10% or less, are not significant, and oils within that range can be considered approximately equivalent.
*** All oil bottles were thoroughly shaken before the samples were taken. This ensured that all the additive package components were distributed uniformly throughout all the oil in the bottle, and not settled to the bottom.
*** All oils are full synthetic unless otherwise specified.
*** All oils are suitable for street use unless otherwise specified.
Oil categories:
*** Over 90,000 psi = OUTSTANDING protection
*** 75,000 to 90,000 psi = GOOD protection
*** 60,000 to 75,000 psi = MODEST protection
*** Below 60,000 psi = UNACCEPTABLE protection
********** OUTSTANDING PROTECTION ************
1. 5W30 Pennzoil Ultra, API SM = 115,612 psi
I have not been able to find this oil with the latest API SN certification. The bottle says, “No leading synthetic oil provides better wear protection”. For once, a product’s hype turns out to be true.
zinc = 806 ppm
phos = 812 ppm
moly = 66 ppm
2. 10W30 Lucas Racing Only = 106,505 psi
zinc = 2642 ppm
phos = 3489 ppm
moly = 1764 ppm
NOTE: This oil is suitable for short term racing use only, and is not suitable for street use.
3. 5W30 Mobil 1, API SN = 105,875 psi
zinc = 801 ppm
phos = 842 ppm
moly = 112 ppm
4. 0W30 Amsoil Signature Series 25,000 miles, API SN = 105,008 psi
zinc = 824 ppm
phos = 960 ppm
moly = 161 ppm
******* 10% below number 1 = 104,051 psi ********
5. 10W30 Valvoline NSL (Not Street Legal) Conventional Racing Oil = 103,846 psi
zinc = 1669 ppm
phos = 1518 ppm
moly = 784 ppm
NOTE: This oil is suitable for short term racing use only, and is not suitable for street use.
6. 5W50 Motorcraft, API SN = 103,517 psi
zinc = 606 ppm
phos = 742 ppm
moly = 28 ppm
7. 10W30 Valvoline VR1 Conventional Racing Oil (silver bottle) = 103,505 psi
zinc = 1472 ppm
phos = 1544 ppm
moly = 3 ppm
8. 10W30 Valvoline VR1 Synthetic Racing Oil, API SL (black bottle) = 101,139 psi
zinc = 1180 ppm
phos = 1112 ppm
moly = 162 ppm
9. 5W30 Chevron Supreme conventional, API SN = 100,011 psi
This one only costs $4.29 per quart.
zinc = TBD
phos = TBD
moly = TBD
10. 5W20 Castrol Edge with Titanium, API SN = 99,983 psi
zinc = TBD
phos = TBD
moly = TBD
titanium = TBD
11. 20W50 Castrol GTX conventional, API SN = 96,514 psi
zinc = 610 ppm
phos = 754 ppm
moly = 94 ppm
12. 30 wt Red Line Race Oil = 96,470 psi
zinc = 2207 ppm
phos = 2052 ppm
moly = 1235 ppm
NOTE: This oil is suitable for short term racing use only, and is not suitable for street use.
13. 0W20 Mobil 1 Advanced Fuel Economy, API SN = 96,364 psi
zinc = TBD
phos = TBD
moly = TBD
14. 5W30 Quaker State Ultimate Durability, API SN = 95,920 psi
zinc = 877 ppm
phos = 921 ppm
moly = 72 ppm
15. 5W30 Castrol Edge with Titanium, API SN = 95,717 psi
zinc = 818 ppm
phos = 883 ppm
moly = 90 ppm
titanium = 44 ppm
16. 10W30 Joe Gibbs XP3 Racing Oil = 95,543 psi
zinc = 743 ppm
phos = 802 ppm
moly = 1125 ppm
NOTE: This oil is suitable for short term racing use only, and is not suitable for street use.
17. 5W20 Castrol GTX conventional, API SN = 95,543 psi
zinc = TBD
phos = TBD
moly = TBD
NOTE: Oil numbers 16 and 17 were tested weeks apart, but due to the similarities in their wear scar sizes, their averages ended up the same.
18. 5W30 Castrol GTX conventional, API SN = 95,392 psi
zinc = TBD
phos = TBD
moly = TBD
19. 10W30 Amsoil Z-Rod Oil = 95,360 psi
zinc = 1431 ppm
phos = 1441 ppm
moly = 52 ppm
20. 5W30 Valvoline SynPower, API SN = 94,942 psi
zinc = 969 ppm
phos = 761 ppm
moly = 0 ppm
21. 5W30 Valvoline Premium Conventional, API SN = 94,744 psi
zinc = TBD
phos = TBD
moly = TBD
22. 5W20 Mobil 1, API SN = 94,663 psi
zinc = TBD
phos = TBD
moly = TBD
23. 5W20 Valvoline SynPower, API SN = 94,460 psi
zinc = TBD
phos = TBD
moly = TBD
******** 20% below number 1 = 92,490 psi ********
24. 5W30 Lucas conventional, API SN = 92,073 psi
zinc = TBD
phos = TBD
moly = TBD
25. 5W30 O'Reilly (house brand) conventional, API SN = 91,433 psi
This one only costs $3.99 per quart.
zinc = TBD
phos = TBD
moly = TBD
26. 5W30 Red Line, API SN = 91,028 psi
zinc = TBD
phos = TBD
moly = TBD
27. 5W20 Royal Purple API SN = 90,434 psi
zinc = TBD
phos = TBD
moly = TBD
28. 5W20 Valvoline Premium Conventional, API SN = 90,144 psi
zinc = TBD
phos = TBD
moly = TBD
************ GOOD PROTECTION **********
29. 30 wt Castrol Heavy Duty conventional, API SM = 88,089
zinc = TBD
phos = TBD
moly = TBD
30. 10W30 Joe Gibbs HR4 Hotrod Oil = 86,270 psi
zinc = 1247 ppm
phos = 1137 ppm
moly = 24 ppm
31. 5W20 Pennzoil Ultra, API SM = 86,034 psi
I have not been able to find this oil with the latest API SN certification.
zinc = TBD
phos = TBD
moly = TBD
32. 5W30 Royal Purple API SN = 84,009 psi
zinc = 942 ppm
phos = 817 ppm
moly = 0 ppm
33. 20W50 Royal Purple API SN = 83,487 psi
zinc = 588 ppm
phos = 697 ppm
moly = 0 ppm
34. 5W30 Mobil 1 Extended Performance 15,000 mile, API SN = 83,263 psi
zinc = 890 ppm
phos = 819 ppm
moly = 104 ppm
35. 0W20 Castrol Edge with Titanium, API SN = 82,867 psi
zinc = TBD
phos = TBD
moly = TBD
******** 30% below number 1 = 80,928 psi ********
**************** MODEST PROTECTION ************
36. 5W30 Royal Purple XPR (Extreme Performance Racing) = 74,860 psi
zinc = 1421 ppm
phos = 1338 ppm
moly = 204 ppm
NOTE: This particular bottle of oil was just opened, but was out of a 3 ½ year old case.
37. Brad Penn, Penn Grade 1 Nitro 70 Racing Oil (semi-synthetic) = 72,003 psi
zinc = TBD
phos = TBD
moly = TBD
38. 0W30 Brad Penn, Penn Grade 1 (semi-synthetic) = 71,377 psi
zinc = 1621 ppm
phos = 1437 ppm
moly = 0 ppm
39. 10W30 Brad Penn, Penn Grade 1 (semi-synthetic) = 71,206 psi
zinc = 1557 ppm
phos = 1651 ppm
moly = 3 ppm
40. 15W50 Mobil 1, API SN = 70,235 psi
zinc = 1,133 ppm
phos = 1,168 ppm
moly = 83 ppm
******** 40% below number 1 = 69,367 psi ********
41. 5W30 Motorcraft, API SN = 68,782 psi
zinc = 796 ppm
phos = 830 ppm
moly = 75 ppm
42. 10W30 Royal Purple HPS (High Performance Street) = 66,211 psi
zinc = 1774 ppm
phos = 1347 ppm
moly = 189 ppm
43. 10W40 Valvoline 4 Stroke Motorcycle Oil conventional, API SJ = 65,553 psi
zinc = 1154 ppm
phos = 1075 ppm
moly = 0 ppm
44. Royal Purple 10W30 Break-In Oil conventional = 62,931 psi
zinc = TBD
phos = TBD
moly = TBD
******** 50% below number 1 = 57,806 psi ********
Summary:
Readers can of course do whatever they want with these results. But for me, seeing is believing. The smallest wear scars created by the best oils, were quite impressive. So, now I’ll be choosing oils for my Hotrods and daily drivers from the OUTSTANDING PROTECTION category, in order to have the highest level of protection. There are plenty of different oils in this category, 28 of the 44 to be exact, and they all have 90,000 psi or higher capability. After reading this report, you may never think about motor oil the same way again.
