I used to send my oil out to be tested about 20 years ago, it always came back usable. I really didn't learn much other than the oil was still good and I was wasting money on oil testing. I guess that's why I run the miles that I do on motor oil.

I own a oil company, you would think I'd be preaching 3000 mile oil changes. lol

BTW as soon as I dump new oil in a diesel crankcase and start the motor, it turns black. You can't tell anything by looking at it.IMO