I had my engine oil tested by Blackstone Labs just to see how good my '02 STS engine with 34,660 miles was running. I changed the oil at 8,461 miles, and the OLM had around 12% life remaining. It was getting near the recommended year, so I decided to change it on that account. I use 5W-30 Mobil 1, and here's the results:
"This initial sample from your GM engine turned up nothing unusual. Wear read around averages for this type of engine, which is a very good indication of normal wearing parts. The universal averages show normal wear after 5,200 miles on the oil. Insolubles (oil oxidation and soot due to heat, use and blow-by) were fine at 0.3%, showing good oil filtration. The TBN read 3.2, still active additive left. No fuel dilution or anti-freeze was found. Silicon was normal at 13 ppm, so your air filtration is getting the job done. Looks good! Try 9,500 miles next time."
I use AC Delco oil filters, and in contrary to what some here say, my K&N air filter appears to be doing a good job of keeping dirt out of the engine! They even commented on it! The wear additives were still good. I'm not sure if that's due to using Mobil 1, or just the nature of the engine. I thought it was amazing that even though I beat this engine hard, the oil was still in good shape with nearly 8,500 miles, and they suggested waiting another 1,000 to change it next time!
The basic test was $20, but I added the TBN for another $10. It's not something I think I'll do everytime, but once in a while to see how the engine is doing. I really want to do my '94 Deville with the 4.9 next. It has 132,000 miles, so it'll be interesting to see how good that engine is.
