Happy New Year-

Changed the oil today in my 1990 Century w/the Iron Duke 2.5. Car has about 78K miles and I drained out 5W-20 and put back 2 quarts of 5W-30 and the rest (appx. 1.75 qts) of 5W-20, long story why. Replaced filter too with some Chinese POS I got from Rock Auto.

Drove vehicle on the highway for about 5 miles and got the oil light flickering at low RPM's when returning to town, revving vehicle probably above about 1000 RPM's makes it go out. WTH?

My Hayne's manual makes no mention of the oil pressure sender other than in the wiring diagram. I have not gotten back underneath to see where it is located. Is this just a strange coincidence of the oil change and now this? Open for suggestions, to begin with where is the sending unit located on this engine?