Oil Pressure Guage 1993 300E 2.8
 

The needle would rise and fall with acceleration and deceleration of the engine. After I changed the oil the needle is at 2 while the car is cold but as soon as it warms up the needle drops to 0 and stays there. Could I have busted something when I changed the oil. The oil that came out was thicker than what I replaced it with, could this be a factor

What weight oil did you put in? How much?

Not likely. By the way, when the oil presuure sender fails, the needle pegs to "3" the instant you turn the ignition key (without even starting the engine) and remains there until you turn the car off.

If the oil pressure gauge acted fine prior to the oil change, the lighter oil weight could certainly be a factor.

I run 10W-30, and my gauge reads "3" on startup, then eventually settles at around "2" at idle when fully warmed up...

Not necessarily....my failing sensor read low and was erratic. The one I changed it out with worked fine for 1.5 days, then failed. Dead gauge, never moved off 0. Replaced with a VDO (better) and it has worked flawlessly since. So they don't always fail pegged at 3, depends which way they fail.

newbenzer, not sure of the ambient temperature where you live, but the factory fill for that vintage engine was 15W40 mineral oil. I run Mobil 1 15W50 synthetic oil in similar engines year round. Check the Owner's Manual chart for the proper weight oil vs. ambient temperature.