Could anyone give me a answer to why my oil guage jumps between 18 to 35? I just replaced the sending unit because the guage was pegged at 120 all the time. The engine is a 2000 3800 supercharged. Please help. I'm getting very worried it may be something bigger than the car is worth.

Does it fluctuate when your rpms go up and down?

Yes, but it also goes up and down at a steady idle