I have been testing all of my vehicles for several years now. I installed a Fumato valve on each vehicle, including the Beaver and send a sample off with each oil change on most of them, particularly the diesels. So far, I have been alerted with a buiding problem in a 6.0 Powerstroke Diesel in a F250, which I no longer possess, and was very happy to have a solid track record of oil changes and engine condition in the Contessa when the engine blew at 19,000 miles. I was able to provide the repair shop with copies of the test results, which showed absloutely no issues, when the coach was towed into Fairbanks. Cummins never questioned the warranty coverage. It's cheap piece of mind.