Originally Posted by Edmund944
so how exactly would i go about manually testing the oil pressure myself just to verify that it is really fluctuating as much as the gage says? And where can I go about finding a new sending unit? How hard is it to replace?
Not hard; it just screws in. I have not done this replacement on a Bonneville, but usually you unscrew them via a line wrench or open-end wrench around the base of the sending unit, or via a special sending-unit socket that you can buy for a few bucks, depending on how easy it is to get at.
I hate to say this but unless the sending unit is obviously wet on the outside and/or leaking, your problem is more likely to be a failing oil pump than a bad sending unit. Going to a heavier weight of oil can stave off the inevitable for a short while, but not long.
Some engines, particularly Oldsmobiles, have a habit of eating their oil pressure idiot lights or sending units, but not Bonnevilles. On the other hand, you do need to verify correct oil pressure readings anyway before tearing the engine apart. Good luck.