So I pulled my lab results from this winter's test. I last changed my
oil two years ago and that was less that 2,000 miles. All wear element PPM values were well below "normal" readings. Remember that I have a solid flat tappet cam, so
zinc and phosphorous are extra important. My
zinc number was 1722 and my phosphorous number was 1640. Perfect. My
antifreeze and water numbers were both at zero. Fuel was at a trace level. My TBN was at 8.8; my Brad Penn right out of the bottle is at 10.6 -- so I'm at 83%. A
conservative change point for TBN is at 70%. There were no red, nor yellow, flags on the analysis sheet. So, why would I even
think about changing my
oil? That's like putting someone on a vitamin supplement when they have perfectly normal bloodwork.
Nice little article on TBN and change intervals can be found here:
https://www.machinerylubrication.com...terval-tan-tbn