Check Oil

When my 1996 Olds 88LS with 111500 miles sits for about 24 hours, the Check Oil Level light will come on when I start it and won't go off until I get to about 50MPH. The dipstick shows full level. Any ideas why the light would come on and not go off until around 50MPH?

I changed out my low oil sensor on front side of pan toward bottom of pan and it corrected the problem. Cost for sensor was around $65.00. Part# 25626343 from GM.

I had this problem and it was the oil pressure sending unit.
At stop lights my oil pressure guage would drop to zero and the alarm would go off. I had to race the engine to get some oil pressure. This worried the heck out of me until I replaced the sender. I actually had good oil pressure all the time.