WHY Mechanic says no oil car runs but makes noise oil light did not come on?

i will answer it as best as I can. With all computer systems in cars their are always differences in the features and what your computer will tell you with lights. If you car did come equipped with a sensor to check for low oil it may be damaged in some way or you do not have one at all and seeing as it is a saturn I would not doubt that at all. Typically when you engine starts to make a lot of noise the oil is the first thing you will want to check. Your car manual will give specific instructions on how to check your oil but for the most part they are all the same..... You will want to warm your car to operating temperatures by running it a few minutes than shut it off. Ensure your car is on a level surface before checking your oil. Open your engine compartment and locate your oil dipstick (have a small rag handy). Remove the dipstick and wipe the level indicator with a small rag than replace the dipstick. Remove it again but this time turn the dipstick horizontal to the ground to check the level of the oil. Add oil as needed but do not over fill... continually check your oil level as you progressively fill it with the recommended oil. Do not rely on sensors and lights as they can malfunction or do not check the things you may expect them to.

If it doesn't have oil, check bulb for oil light in dash. just replace temporarily with a known good one. If that works, buy a bulb, if not have mech check sending unit and confirm you do indeed have oil pressure. It is rare but pump could be out.