I have a 2000 Expedition that I bought last November. At that time when I started the truck the oil pressure guage would be all the way down and the light there would light up. As I drove the truck the guage would flick up and down, each time it would go up the light would go off. After about three miles of driving the guage would go all the way up and the light would go off and it would stay that way for the rest of the drive. As the weather got warmer this stopped happening until about a week ago when it came back. I change the oil every three to four thousand miles and check the level weekly. Any ideas what would cause this.

Thanks.

 

Bad sending unit, bad wiring, bad ground...

The oil pressure guage in this model does not show gradual and incremental changes in pressure. Think of it as a three-speed guage, limited to low, medium and high.

 

Actually, it's just a simple on-off pressure switch. When the oil pressure switch goes above 4-5 psi, the switch closes and the guage reads mid-scale and the idiot light goes out.

The OP has a sending switch that is going bad. Time for a new one at the next oil change. Actual location depends on which engine is in use, but generally, it will screwed into a block at or near the oil filter.

Steve