540 RAT wrote:razor66 wrote:Any thoughts on why there would be so much difference in the results from your testing between these two oils that look to be the same brand other than the viscosity weight rating?
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
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
Yeah, that was one of the surprises during the testing. Not all like brand oils fell into line like you might expect. But repeat testing at different times showed the same results over and over again. So, the numbers are what they are. Only the oil company in question or a very expensive forensic lab test could reveal for sure why they are different.
Though in some of my conversations with the Royal Purple Engineers, they told me that the technology is not in place to absolutely guarantee that oil from different batches will be "exactly" the same. And that normal lab tests may show differences even for oil that would otherwise seem like it should be identical.
Their statement really surprised me, because I thought in this modern 21st Century computer controlled age we live in, that everything "would be" identical. So, perhaps that may account for the differences. And that's all the more reason to do the kind of testing I did. That way you don't have to just "assume" that similar oils will have similar capabilities. I plan on testing the oil I use, maybe once a year to see if it is still similar to what it was before.
And speaking of repeat testing at different times showing the same results over and over again. I was so shocked that the winning 5W30 Pennzoil Ultra, API SM, could be so good, that I tested it probably twice as many times as I tested all the other oils. And every time it tested extremely well. It simply would NOT test bad. It really is good oil, and I will be putting it in my own 800 HP, 540ci BBC.
Yes, I was definitely surprised to see that much difference (~30,000 psi) with just such a small change in the viscosity between the two. I would also think that they would have tighter control from batch to batch, but perhaps not and that may be where the difference lies. Your spot testing should detect this if you start seeing significant changes in the results from the 5W30 you plan to use. I would of course like to have seen the results between these two weights of the same oil closer to one another as some may want or need to run a different weight oil in their engine and depending on this the Penzoil Ultra, API SM might very well not be the better choice. I look forward to seeing some more of your future testing results. Thanks for posting them.