Folks know this has been talked to death, but Mobil is claiming 15K miles on this stuff. Mobil One Truck and SUV Synth Oil 5w-40W. I know the filter needs to be changed at 5K. And that the best way is to test the oil. My question is what to test for, who to test, and how to test. Ok, that 3 questions.

Thanks,
Donnie