I’ve been running my car at “zero” oil pressure because my mechanic told me that the sending unit was just broke and I assumed he was right because it was running fine. My gauge magically works again all of a sudden and Now he’s telling me I have really low compression and I’m wondering if it’s because I was running at zero.

would there be any noticeable change when running at zero oil pressure?

 

if the engine(any engine) was actually running zero oil pressure, it would seize up in less than 5 min. probably just a poor connection due to corrosion since it "magically" started working. sounds like the mechanic doesn't really know and he's just guessing.