I've noticed that in the past couple days, my oil pressure has been a lot higher than usual. It normally runs about 20psi at idle and 40psi at normal cruising RPMs (1200-2000 RPMs). However, lately it's been about 40psi at idle and around 60psi at crusing RPMs. The gauge still returns to 0psi when the engine is off, and it seems to fluctuate with engine speed as it should, it's just that the numbers are way off. It's a stock vortec 350, stock oil pump/gauge, and the oil level is good. What's the deal?