https://540ratblog.wordpress.com/The test methodology or test procedure I use at a representative operating oil temperature of 230*F, is a dynamic rubbing friction test under load, which generates a wear scar on a test specimen that is bathed in the oil being tested. This procedure, which is performed exactly the same for every motor oil tested, provides excellent repeatability, which is critical to validate the methodology. (...) So, the result is pounds per square inch, which of course is just shortened to “psi”. The better an oil’s wear protection capability, the smaller the wear scar will be on the test specimen, and the higher the resulting psi value will be. Multiple tests are performed on each oil, and the resulting values are averaged to arrive at the most accurate possible value for comparison. And the motor oils are ranked, based on the average psi value they generated.
4. 5W30 Mobil 1, Advanced Full Synthetic, API SN, GM dexos 1 approved = 117,799 psi
42. 0W20 Mobil 1 Advanced Fuel Economy, API SN synthetic = 96,364 psi
76. 5W50 Mobil 1, API SN, synthetic = 86,456 psi
Thicker oils DO NOT automatically provide better wear protection than thinner oils, as some people mistakenly believe. Extensive “dynamic wear testing under load” of over 170 motor oils, has shown that the base oil and its additive package “as a whole”, with the primary emphasis on the additive package, which is what contains the extreme pressure anti-wear components, is what determines an oil’s wear protection capability, NOT its viscosity. In fact, the test data has shown that 5W20 oils can provide INCREDIBLE wear protection with over 120,000 psi load carrying capability/film strength/shear resistance, while 15W50 oils can sometimes only provide UNDESIRABLE wear protection with less than 60,000 psi. So, DO NOT use thicker oil under the assumption that it can provide better wear protection for our engines, because that is simply NOT TRUE.
Capability ranking at 275*F:
1. 5W30 Pennzoil Ultra, API SM = 97,955 psi (dropped 15% from its 230* value)
2. 5W30 Mobil 1, API SN = 96,323 psi (dropped 9% from its 230* value)
(2% below no. 1 here at 275*)
4. 5W50 Motorcraft, API SN = 92,545 psi (dropped 11% from its 230* value)
(6% below no. 1 here at 275*)
6. 20W50 Castrol GTX, API SN = 85,815 psi (dropped 11% from its 230* value)
(12% below no. 1 here at 275*)
7. 5W20 Castrol Edge w/Titanium, API SN = 84,584 psi (dropped 15% from its 230* value)
(14% below no. 1 here at 275*)
11. 0W30 Brad Penn, Penn Grade 1 = 68,768 psi (dropped ONLY 4% from its 230* value)
(30% below no. 1 here at 275*)