James my 2003 BMW 320i oil light comes on when the engine gets up to operating temperature. I changed the oil sending unit replaced and I still have the same problem. I am scratching my head wondering, “Does this mean my engine is worn out?”
Oil light coming on at idle could mean you have low engine oil pressure, which MAY mean a worn out engine. It could mean you have a NEW faulty oil pressure switch. To verify what the problem is, you need to have a mechanical oil pressure gauge installed in place of the oil sending unit for testing purposes. By doing this type test you are verifying the actual oil pressure of your car’s engine, when it is up to operating temperature, in gear, at idle.
I researched on my computer data base what the minimum oil pressure should be on your vehicle. It should be 7.25 PSI or higher in gear, sitting still. If, on the test drive the oil pressure drops to 7.25 lbs or lower, you may have an internal mechanical problem that needs to be corrected. What I suspect your problem is the NEW oil sending unit that was installed on your car. I suspect it is an aftermarket oil sending unit that is not properly calibrated to the specifications of your car. If you do find the oil pressure is above 7.25 lbs at idle, at operating temperature, then I suggest replacing this new (defective) oil sending unit with a factory BMW oil sending unit. I believe this will solve your problem that has got you scratching your head.
Peace and prosperity to you and yours,
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