my friend just bought the 91 oldsmobile 88 that ive been lookin at forever for $800 from the dealer i bought my jeep from, its silver with power everything, driver information system, etc etc etc basically its loaded.

today on the drive home from the dealer i noticed that the oil pressure gauge was only at 1/4 during the whole trip and the driver info system was said exactly like this: CHANGE OIL NOW

so we changed the oil (10w30 Havoline regular cuz we didnt know if it had any leaks to go to synthetic or not) and after the startup the oil pressure gauge went wild, it was all over the place so im passing it off as a bad sending unit, the engine runs excellent with tons of power, and the trans is a new gm factory rebuilt unit with real smooth shifts.

now for the wierd part, we took it out again after the change and on our way back from burger king, the gauge bottomed out and the chimer threw a fit, DING DING DING DING DING....etc etc etc, now the engine the whole time is running excellent with no power loss/hesitation/wierd noises nuttin, just a smooth running 3800.

so my question is, is it the sending unit, or is the engine on its way out???

ps. its a 3800 with 131k on it

is there a chance that u have to reset something after u do the oil change?

i know u have to reset the driver info sys for an accurate change oil reading (dont know how to tho ), but that wouldnt have anything to do with the pressure gauge bottoming out

Just to be safe, I would hook up a mechanical oil pressure gauge, but it sounds like the sender is bad.

As for the oil change reminder, you reset it by holding down the OIL and RESET buttons together for a few seconds until the display shows 100%.

On most GM cars, to reset the oil change light, you have to turn the key on (but not started) and press the gas pedal to the floor three times (fully release it each time). Then turn the key off. Then start the car. It should be off.