I have been cycling through various brands of motor oil at changes and noticing differences in our 5.3 Tahoe usage.
I've always use the same weight all synthetic oils with the same AC Delco filters and just varied the oil brands.
In the latest brand trial I have noticed a 5 psi drop in idling hot oil pressure (40 down to 35) but a 5 psi increase at 2000 rpm (also hot) from about 50 to 55.
Does it make any sense that a particular oil brand would cause an oil pressure variation?
With the brand immediately before this one I noticed a persist burned oil odor but there are no leaks or stains to be found. The odor is gone with the current brand.
The brand before that seemed to lose (burn off?) more than a quart between oil changes, perhaps at 5000 mile intervals or so.
I don't know if it's the oil but it is odd.
Does this make any sense?
That's odd indeed. Could it be some other factor? I mean that's why they do double-blind tests for medicines and other things.
Could it be different times of the year, and the external temperatures are different? Other than that, I've never done any comparisons like what you are describing, but I suppose... maybe.... could be some differences in the ingredients used? Because I imagine that even though they may be the same viscosity, just sourcing the materials from different sources (synthetic and/or natural) could produce some variations in how the oil behaves.
Hard to do a real side by side analysis for something like that.
