On the Corvette C6, Z06 Forum, perhaps the most popular oil the U.S. guys like to use is what they call, the 0W40 Euro blend Mobil 1. This oil is what GM calls for in the Owner’s Manual and also on the oil filler cap on C6 Z06's sold in Canada and Europe, whereas 5W30 Mobil 1 is called for in the U.S. The rationale the U.S. Corvette owners typically use for choosing this 0W40 Euro blend Mobil 1 instead of following GM’s recommendation, is the thinking that this oil may have more zinc than U.S. oil, and their mistaken belief that more zinc and a higher viscosity can provide better wear protection, as well as their mistaken belief that 5W30 Mobil 1 is not very good.
Also, on “Bob is the Oil Guy” Forum, 0W30 Castrol Edge with Syntec (black bottle), API SL, European Formula, made in Germany and sold in the U.S., is very popular. This is apparently because they favor the better cold flowing 0W cold viscosity rating (which is a good idea), and because of the thinking that this oil may have more zinc than U.S. oil, and their mistaken belief that more zinc can provide better wear protection.
The Z06 guys as well as the Bob Forum guys, obviously feel this way based on emotion and guessing/speculation, because they clearly never had any test data to evaluate………………until now. The details on that below.
I've performed accurate and repeatable motor oil "Dynamic Wear Testing Under Load", which more specifically is a rubbing friction test under load, on about 120 different oils so far. Below is how high and low zinc motor oils compared with regard to Wear Protection Capability (the oil providing the best protection ranks number 1):
* High zinc oils rank between number 5 and number 124, which VERY CLEARLY shows that simply having a high level of zinc is no guarantee of superior wear protection. If a high level of zinc was a guarantee of superior wear protection, then all high zinc oils would rank at the top of the list. But, that simply is NOT the case. And in traditional older style engines, many wiped flat tappet lobes COULD HAVE BEEN AVOIDED if people had not blindly believed that all high zinc oils provide all the wear protection they need. Because nothing could be further from the truth.
* Low zinc oils rank between number 1 and number 100.
* Since the low zinc oils and the high zinc oils completely overlap, you can see that zinc does not play the primary role in determining an oil’s wear protection capability. An oil’s wear protection capability is determined by its base oil and its additive package “as a whole”, with the primary emphasis on the additive package, which contains the extreme pressure anti-wear components. Modern alternate extreme pressure anti-wear components are equal to, or better than zinc.
And consider the following:
1. Well known and respected Engineer and Tech Author David Vizard, whose own test data, largely based on real world engine dyno testing, has concluded that more zinc in motor oil can be damaging, more zinc does NOT provide today's best wear protection, and that using zinc as the primary anti-wear component, is outdated technology.
2. The GM Oil Report titled, "Oil Myths from GM Techlink", concluded that high levels of zinc are damaging and that more zinc does NOT provide more wear protection.
3. A motor oil research article written by Ed Hackett titled, "More than you ever wanted to know about Motor Oil", concluded that more zinc does NOT provide more wear protection, it only provides longer wear protection.
4. This from the Brad Penn Oil Company:
There is such a thing as too much ZDDP. ZDDP is surface aggressive, and too much can be a detriment. ZDDP fights for the surface, blocking other additive performance. Acids generated due to excessive ZDDP contact will “tie-up” detergents thus encouraging corrosive wear. ZDDP effectiveness plateaus, more does NOT translate into more protection. Only so much is utilized. We don’t need to saturate our oil with ZDDP.
My test results came up with the exact same results stated by all four of those independent sources. So, this is an example where motor oil “Dynamic Wear Testing Under Load” using oil testing equipment, engine dyno testing, Motor Oil Industry testing, and proper motor oil research using only the facts, from a total of five (including my own) independent sources, all converged to agree and come to the same exact conclusion. Back-up validation proof, doesn't get any better than this.
The ONLY way to tell how well an oil can protect against wear, is to perform dynamic wear testing under load, at a representative operational temperature, in order to determine its “Load Carrying Capacity/Film Strength”. And that is precisely what I’ve done over the past couple of years. And the test equipment has its calibration checked and adjusted if needed, each time the testing switches to a different oil. That way excellent accuracy is maintained at all times.
Not only does my test data match the independent sources above, but my oil testing methodology and the resulting data have also been endorsed by the following well respected sources:
1. Dr. Lars Grimsrud, who is the most highly respected Engineer, Car builder and Tech Guru on the Corvette C3 Forum. He told me, “I'm 100% on board with backing you with my endorsement on your testing: I run a Propulsion Testing Laboratory for a major Aerospace Company, so I'm in the testing business. Your methods and approach are in accordance with sound engineering testing methods, and are not arguable by intelligent people”. He also told me this about my Oil Testing info, “This is excellent stuff, and I've already sent copies of this to my engineering colleagues”. In addition to that, he now includes my Oil Testing Info in a list of Tech Papers written by well respected Industry authors, that he makes available to enthusiasts.
2. A NASCAR engine supplier out of North Carolina (they did not want their name associated with any Internet motor oil arguments that may come up, so they asked that their name be left out, which I honored) was so impressed with the motor oil “Wear Protection Capability Testing” I perform, that they sent me 3 NASCAR Racing Oils they use, for testing. They valued my testing efforts enough to include me in what they do, which is quite an endorsement, considering the Professional level of Racing they are involved in. They had been seeing some wear issues with those oils, and wanted to see if I could shed any light on that by testing them. I did test those oils for them, and the test results showed that those oils did not provide acceptable wear protection capability, which accounted for the wear problems they were having. So, they have selected other oils to use, and their wear problems have gone away. If I had tested those oils before they started using them, I could have saved them time, money and grief.
3. The “Oil Extreme” Oil Company was so impressed with the detail and accuracy of my oil testing, that they wanted to hire me to perform product development research testing for them. That was clearly a major endorsement of the testing I perform. But, I declined taking any money from them, because I won’t be tied to any Oil Company by money. That way I can maintain my independent and unbiased status. I report the test results just how they come out, good or bad. And there is no way I’d allow any Oil Company to influence anything I report. I did however, agree to perform testing for them for free, along with other testing I perform. And those results will be posted along with other test results.
Below is how the various viscosities compared with regard to Wear Protection Capability:
* 20 wt oils rank between number 17 and 116
* 30 wt oils rank between number 1 and 124
* 40 wt oils rank between number 54 and 115
* 50 wt oils rank between number 10 and 108
So, as you can see, oil viscosity plays no particular role in an oil’s wear protection capability. An oil’s wear protection capability is determined by its base oil and its additive package “as a whole”, with the primary emphasis on the additive package, which contains the extreme pressure anti-wear components.
CONSIDER THE BENEFITS OF USING THINNER OIL:
• Thinner oil flows quicker at cold start-up to begin lubricating critical engine components much more quickly than thicker oil can. Most engine wear takes place during cold start-up before oil flow can reach all the components. So, quicker flowing thinner oil will help reduce start-up engine wear, which is actually reducing wear overall.
• The more free flowing thinner oil at cold start-up, is also much less likely to cause the oil filter bypass to open up, compared to thicker oil. Of course if the bypass opened up, that would allow unfiltered oil to be pumped through the engine. The colder the ambient temperature, and the more rpm used when the engine is cold, the more important this becomes.
• Thinner oil also flows more at normal operating temperatures. And oil FLOW is lubrication, but oil pressure is NOT lubrication. Oil pressure is only a measurement of resistance to flow. Running thicker oil just to up the oil pressure is the wrong thing to do, because that only reduces oil flow/lubrication. Oil pressure in and of itself, is NOT what we are after.
• The more free flowing thinner oil will also drain back to the oil pan quicker than thicker oil. So, thinner oil can help maintain a higher oil level in the oil pan during operation, which keeps the oil pump pickup from possibly sucking air during braking and cornering.
• The old rule of thumb that we should have at least 10 psi for every 1,000 rpm is perfectly fine. Running thicker oil to achieve more pressure than that, will simply reduce oil flow for no good reason. It is best to run the thinnest oil we can, that will still maintain at least the rule of thumb oil pressure. And one of the benefits of running a high volume oil pump, is that it will allow us to enjoy all the benefits of running thinner oil, while still maintaining sufficient oil pressure. A high volume oil pump/thinner oil combo is preferred over running a standard volume oil pump/thicker oil combo. Because oil “flow” is our goal for ideal oiling, NOT simply high oil pressure.
• Oil flow is what carries heat away from internal engine components. Those engine components are DIRECTLY oil cooled, but only INdirectly water cooled. And better flowing thinner oil will keep critical engine components cooler because it carries heat away faster. If you run thicker oil than needed, you will be driving up engine component temps.
• Thinner oil will typically increase HP because of less viscous drag and reduced pumping losses, compared to thicker oils. That is why very serious Race efforts will generally use watery thin oils in their engines. But, an exception to this increase in HP would be in high rpm hydraulic lifter engines, where thinner oil can allow the lifters to bleed-off at higher rpm. In everyday street vehicles, where fuel consumption is a consideration, thinner oils will also typically increase fuel economy. The majority of new cars sold in the U.S. now call for 5W20 specifically for increased fuel economy. And now Diesel trucks are increasingly calling for 5W30, also for fuel economy improvement.
• With the exception of high rpm hydraulic lifter engines, almost no engine should ever need to run oil thicker than a multi-viscosity 30 weight. The lower the first number cold viscosity rating, the better the cold flow. For example, 0W30 flows WAY better cold than 20W50. And 0W30 flows WAY better “cold” than straight 30wt, which is horrible for cold start-up flow and should be avoided at all cost. And the lower the second number hot viscosity rating, the better the hot flow. For example, 0W30 flows WAY better “hot” than 20W50.
• Thicker oil DOES NOT automatically provide better wear protection than thinner oils. Extensive “dynamic wear testing under load” of dozens and dozens of motor oils, has shown that the base oil and its additive package “as a whole”, is what determines an oil’s wear protection capability, NOT its viscosity. For example, some 5W20 oils have proven to provide OUTSTANDING wear protection, while some 15W50 oils have only been able to provide MODEST wear protection. So, do not run thicker oil under the false assumption that it can provide better wear protection for our engines.
• BOTTOM LINE: Thinner oils are better for most engine lubrication needs.
Now, on with the main purpose of this write-up. All this calls for testing those 0W40 and 5W30 Corvette Z06 oils, as well as testing 0W30 oils, to see how they all compare. Then Z06 owners and the Bob Forum guys can take a look at actual hard numbers that will show the facts. With that information in hand, they can make an informed decision when it comes to selecting an oil that will truly provide them with the best wear protection.
So, I tested the following motor oils:
0W40 and 5W30 Pennzoil Ultra
0W40, 5W30 and 0W30 Mobil 1
0W40, 5W30 and 0W30 Castrol Edge with Syntec (in the black bottle)
NOTE: Castrol’s top of the line 100% Edge motor oil, comes in the gold bottle.
The Wear Protection reference categories are:
• Over 105,000 psi = INCREDIBLE wear protection
• 90,000 to 105,000 psi = OUTSTANDING wear protection
• 75,000 to 90,000 psi = GOOD wear protection
• 60,000 to 75,000 psi = MODEST wear protection
• Below 60,000 psi = UNDESIRABLE wear protection
Here is how these oils ranked just among themselves, according to their Wear Protection Capability. All wear protection capability testing was performed at 230* F, and the higher the psi value, the better the wear protection. I also included values for the onset of thermal breakdown for comparison (the thermal breakdown values were rounded to the nearest 5* increment):
1. 5W30 Pennzoil Ultra, API SM synthetic = 115,612 psi, which puts it in the INCREDIBLE wear protection category.
The onset of thermal breakdown = 280* F
2. 5W30 Mobil 1, API SN synthetic = 105,875 psi, which puts it in the INCREDIBLE wear protection category.
The onset of thermal breakdown = 265* F
3. 5W30 Castrol Edge w/Syntec, API SN (black bottle, formerly Castrol Syntec) synthetic = 85,179 psi, which puts it in the GOOD wear protection category.
The onset of thermal breakdown = TBD
(I did not test this particular oil for this when I had it on hand)
4. 0W40 Mobil 1, API SN, European Formula, made in the U.S., synthetic = 82,644 psi, which puts it in the GOOD wear protection category.
The onset of thermal breakdown = 285* F
5. 0W40 Pennzoil Ultra, API SN, synthetic = 81,863 psi, which puts it in the GOOD wear protection category.
The onset of thermal breakdown = 260* F
6. 0W30 Mobil 1, API SN, Advanced Fuel Economy, synthetic = 81,240 psi, which puts it in the GOOD wear protection category.
The onset of thermal breakdown = 290* F
7. 0W40 Castrol Edge with Syntec (black bottle), API SN, European Formula, made in Belgium and sold in the U.S., synthetic = 69,307 psi, which puts it in the MODEST wear protection category.
The onset of thermal breakdown = 290* F
8. 0W30 Castrol Edge with Syntec (black bottle), API SL, European Formula, made in Germany and sold in the U.S., synthetic = 69,302 psi, which puts it in the MODEST wear protection category.
The onset of thermal breakdown = 290* F
As you can see from these actual test values, all the 5W30 oils provide better wear protection than any of the 0W oils. But even so, any of these oils would be acceptable for normal daily driver use. However, for highly loaded High Performance applications where the best possible wear protection is desired, the obvious choice would be 5W30 Pennzoil Ultra or 5W30 Mobil 1, which are the only oils in this test that provide INCREDIBLE wear protection.
So, GM got it right about which oil to recommend in their U.S. Z06 Corvette’s. One can only speculate that perhaps they expect the U.S. cars to be run harder, so they call for the best protection in those engines. Although, general availability in Canada and Europe may also play a part in what oil they recommend. Whatever the case, both oil viscosities had to meet GM’s endurance testing requirements.
Folks can of course decide for themselves which oil they want to run in their own cars. But now, they have the accurate test data to make an informed decision.
If you’d like to see how these oils rank in my overall Wear Protection Ranking List, along with additional motor oil tech info, here’s a link:
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