Hello everyone, new the forum. Looks like a great place to get help and help others.

My problem. Son in Law has a 2003 silverado with 100k and it is a pure daily driver short trip vehicle. They are at college and I do not get to see the truck often. We had to trailer it home due to a very bad engine bogging/chugging and the oil is filled with either gas or antifreeze. We took it to Advance Auto for a free read and there was nothing conclusive that indicated an over-active injector or poor F/A ratio's. The spark plugs all look reasonable given the way the truck is driven. Did a pretty inclusive compression test (multiple test per cylinder) with all plugs out, fuel pump relay pulled and held key for three full compression strokes per test. From drivers front to rear cylinder 180, 150, 120, 150. Pass. front to rear - 180, 150, 150, 150.

The first compression stroke on each cylinder was close to 90, 2nd 120 and 3rd either 150 or 180. I am not too concerned with a 120 as the plug looked identical to the others, but, could show some issue.

With these numbers, I do not feel a popped head gasket, rather, an over active or failed injector. Seeking your thoughts on the cylinder pressure numbers. We are taking it to a dealer to scan for more detailed issues, such as, fuel/air ratio, injector balance/rate of activation and whatever else they deem necessary.

Thank you for your time.