I have never had my oil light come on before, but my buddy's 97 Mazda Millenia oil light is on. He said he was over due for a oil change, and got one this afternoon. But his light is still on.

My question is... what can cause the light to go on? Due for a change and low oil pressure? and what would cause that, oil pump, oil sending unit, and a bad gasket?

 

Depends what oil light it is, if its a reminder it may have been triggered by mileage. If its the oil can with a drop of oil coming from it, it probably means low oil pressure, which could mean a lot of things but it should be looked at ASAP and not driven until you verify there is adequate oil pressure.

 

If it's not an oil pressure idiot light...then it's the oil change reminder light.....in which case needs to be reset if the oil change was just completed....look in the owner's manual for how to reset the indicator light.