Originally Posted By: paulri
Never heard about that fleet test before. I'd love to look that up and see what their conclusions were. Do you remember what company, or what engine, or anything?
Originally Posted By: HKPolice
I remember reading about fleets doing tests and sticking with the same brand/type of oil is more important than anything else. Changing oil brands every interval causes more deposits, even with synthetics. You could've used the same brand of conventional oil @ 3-5K intervals and gotten the same clean results.
No published results, just internal tests from a huge fleet. It was mentioned here years ago from a reputable forum member. After testing, the fleet switched all vehicles to the same brand of oil.
The results didn't show any brand being superior or even if synthetics are superior, just that changing brands every interval resulted in more varnish/deposits.
It makes logical sense though, each brand of oil has slightly different add packs. While API standards mean you can mix different brands of oil without causing engine damage, it doesn't say anything about deposits/varnish.