I'm starting to notice when I start my 2001 EXT Cab Duramax that the oil pressure gauge is slow to come up and when the low oil light in the message center comes on the oil pressure gauge jumps up and the light goes out. This has always happened follwing an oil change but to do it know between changes concerns me. It only happens on initial start up of the day and has done it after the truck as sit for several days but also has done it after only one night. Is the oil pump lossing prime? do I have a major problem developing? The truck has 78,000 miles and runs fine.