I have a 1990 F150 with the 302 engine, and since it has started getting cold here the oil pressure gauge is acting funky. Normally when I start the engine the gauge goes to about the middle of the normal range, but when it is cold out, it sits right at the line on the low side of the normal range. The gauge will sit right on the low mark for about 2 or 3 miles and then all of a sudden it pops right over to the middle of the normal range. Any idea why this is doing this? I haven't ever seen this on a vehicle, and this is the first winter I am driving this truck.
TIA
Chris