This is great. I have been suspecting fuel for a while now. I might consider changing the fuel pressure regulator and getting new injectors and probably swap in a new o2 at that point.

Blackstone team, I just wanted to say thank you for offering this service (and for offering it at a reasonable price!). I feel like my kid received good grades on his report card. I will be sending you another sample next summer. Thanks again

I’ve been sending you samples for five years. This report was the first one that spotted trouble. Sure enough, your diagnosis was spot on! It was a leaky intake gasket that was the most likely culprit, also causing the engine trouble light to come on. It seems the problem’s been cured. Should I change the oil again and send another sample after 2000 miles? How about using a synthetic? Again, great work guys.

Had to overhaul my 06 Columbia Freightliner. Thank goodness I took a one year warranty on it! Your samples provided the needed information that something was wrong with the motor. Had a leaking head gasket and two or three of the cylinder liners were leaking as well. Thanks for the good work.