In the last 2 months I've had so many issues with the car its unreal (2003 Bonneville SSEI w/72000 miles). Its a long, complex story so I wont go into it but I've spent 2500 dollars if that tells you anything. I just got my car back from not having it for two weeks and the car SEEMS to be running fine, but I've noticed a couple things. When I start the car, in park, the RPMs are sitting at about 1300, after about 2 minutes of running, in park, the RPMs go back down to about 800. When acclerating the engine seems to be running louder than I ever remember. Seems to be running ok, just seems to be running louder and when it finally hits into 4th gear it gets quieter, I don't know if that the OD or what? But to the problem at hand....when I start the car the Oil Pressure sits around 40 PSI, once I get the car driving and nice and warmed up it will go down to between 20 and 30 psi when I'm at a stop. Once I give the car gas it always goes back up to between 40 and 80 PSI. Its never gotten into the red but it definitely fluctuates and I'm wondering what this is and what I should do about it. Also, I'm using 5 w 30 oil as thats what the engine said it needs and there aren't any noises that I can hear. Any help or suggestions would be appreciated. I just got the car back and I'm going to be taking it back in after I've put 1000 miles on it so they can change the oil and make sure everything is running smoothly, no leaks etc. I'm going to be documenting all these issues so I can tell the mechanic about it when I take it back there but I want to make sure there aren't some serious serious issues here (for as long as my cars been in the shop the last month or so there shouldn't be!!) Thanks in advance

Most likely it'* a bad gauge or sender. You can try replacing the sender, it'* cheap and easy to do, just a little messy but no big deal. Drain the oil and then change the sender. If the pressure drops do low you would hear it.

Dan, thanks for quick response, I will look into that. Am I doing damage to anything currently?

Like Dan said, if the pressure drops too low, you'd hear it. You shouldn't be doing any damage driving it as it is, but it would be a good idea to check the sender like Dan suggested. Another thing I would check is your battery connections. I just had a leaky positive terminal. Right before the battery leaked through enough to completely quit working, I noticed my oil pressure gauge skipping around from 40-ish to 70-ish. After replacing the battery it seems back to normal.

The oil pressure sender replacement is 15 minutes tops for removal and replacement. It'* mounted on the top of the oil filter/pressure regulator plate on the passenger side of the car. Get it up on jacks and get a monster size crescent wrench. I replaced mine without draining the oil, so if you decide to do the same..hauls some rags with you under the car and be quick. Some teflon tape on the threads of the new sender will help prevent leaks.

Thanks for the help guys. If the oil pressure does drop too low what kind of sound am I going to hear?

Lot'* of rattles and bangs.....then followed by a screeching grinding noise and finally total silence

Replace the switch and you can be at ease.

And while hopping in here late, there'* no need to drain the oil to change the sender. Sender is located higher than the oil in the pan. When you pull the sender you will lose a little oil, but not enough to notice on the dipstick.

Thanks for all your help, everyone, I really appreciate it. I've changed my wiper assembly, radiator, spark plugs, wires, and some other things so I feel I'm somewhat car savvy but that all went out the window once I joined the forum. I now realize how much I DON'T know. My last questions is does anyone know a reputable place to find a replacement Oil Pressure Sender and if there is any sort of diagram/guide out there on the net? Thanks again everyone

Go to www.rockauto.com and you should find what you need. Changing it is easy. Just go under the car by the oil filter, the sender is above it. Take some rags and unplug and remove. Put in new one with a little teflon tape plug it in and your all set.