in his lengthy oil analysis, the oil comparison narrowed...
later into the analysis, the focus was reduced to: 0W40 vs 5W30 vs 0W30. And, as it may be difficult to locate in the comprehensive report, it is reprinted here (this may be useful to M-B owners using Mobil 1 0W40, and puzzled by its 75th rank in the larger, all-inclusive list--ultimately, it scored 4th in what is no doubt a more relevant comparison):
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.
All this calls for performing Engineering Wear Protection 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 test data 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 Engineering 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, API SM or 5W30 Mobil 1, API SN, 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.
NOTE: After this piece was originally written, 5W30 Pennzoil Ultra, API “SM” has been phased out and replaced TWICE by a newer API “SN” version. See the Wear Protection Ranking List in Section 1, for the current psi value and ranking position.