Originally Posted by oledoc2u

Here's the real deal. If you were to take an oil, any oil and look at thru a microscope before it is used, then once used, then once refined again, what do you think you would see. Dirt, debri??? You would see all that, from start to finish, but a lot less in the beginning, a whole lot less. It is a refined product from the get go. So, it depends on how good the the refinery is. The addictives will be cooked away over time. So, if additive are re-added to refined oil, maybe have a mediocre oil. Just isn't worth the risk. When managing a fleet of over 100 trucks in my former life, we sent out samples of our higher mileage trucks for testing. Recommend oil changes would range from 10k-25k depending on the truck, and it would give us break downs of metal found in the oil as well as other things. High brass content, would look at main bearings etc etc...We always changed our oil at 10k... I change my own oil in the cars I drive daily every 7k, the XF's once a year, and the rig 10K....Don't skimp on the oil...vecosity is key to long life...that is what breaks down with mileage and heat...wouldn't risk used oil, even though it still has mileage left in it....