Pontiac Repair: Little/no oil after oil change, engine knock Aztek

Question
Hello.  I've got a 2004 pontiac Aztec, with a 3.4L.  Less than 1 month ago, I got my oil changed at a quickie place.  Then, a week and a half ago, my engine starts to knock and miss really bad.  So, I change the plugs, the plug wires, the injector.  Then, I notice that my oil is a bit off.  3.5 quarts low to be exact.  So, the things I do only minimally help.  I take it to a dealer.  They tell me that there is no compression on #3 cyl.  Which is where the miss was.  They're now replacing my motor.  My question is, with out leaking, or burning that much oil, how can I be that low if not for them not filling it all the way?  Also, aren't they responsible for this in some way?  I've only got 88000 miles on it, with oil changes every 4-5000 miles.  I'm kinda stuck here not knowing what went wrong.

Thanks,

Jeff

Answer
Hi Jeff:

Well without seeing this SUV it's hard to say exactly what happened. But from what you have stated it seems a bit fishy. If this has never used "burnt" oil before this last oil change and the engine is not leaking onto the ground then if the engine was 3.5 Qts. low on oil it would indicate it was under filled when the oil was changed and the result was engine failure. It also depends on why the engine was running rough and low on compression. If this had an engine failure first and then the engine started to consume the oil after the failure. It depends on what the engine failure was if something broke in this engine and you continued to drive it it could have been burning the oil and that is why the oil was low. It's sort of what came first the chicken or the egg.. I'd have to know what the failure was to tell you if that could have caused the engine to use the oil.. Good luck :]