I know this has already been discussed here before, but I don't think my problem is the sending unit like Moon replied lower. First, I have a 1992 Cavalier RS (automatic) and when I've been using the car for some time (at least 1 hour) the oil pressure indicator STALLS between 0 and the first quarter of the graduations even when rolling at 100 km/h (2200 RPM). If I stop and rev it up, the indicator doesn't move ! Normally when the car idles with engine running cold, the oil pressure indicator is just a little higher than half (max is 550 on mine) and when I rev it up, the pressure rises a bit. This is why I think it's not my sending unit that is damaged because when the engine is cold, the indicator would be low too, no ? I thought maybe it would be that O-ring in the pump (never changed it), or the pump itself. Anyone had this prob and got it fixed ??? Oh, btw no red light (CHECK GAGES) comes out.