Oil light question
I have a 01 wj 4.7 and was wondering if the oil light would come on for having low oil, and if so how low does the oil have to be? I'm asking Becuase the "new" engine that was put into my car recently stalled out on me and won't start. The mechanic says that it was at least 3.5 quarts low on oil and 1 gallon low on coolant. I know it's complete bull but I need a way to prove it in clue because the mechanic is not following his warrantee because the failure is "my fault"
-2001 WJ Limited, 4.7L V8, Thrush Glasspack muffler dumped before axle(no tailpipe), Spectra CAI,
Rusty's 2" BB