Hello, I was looking for some advice on what weight oil I should be using in my hot rod. I currently have 5w-30 in there now. When the car is cool I have about 40lbs of pressure at idle, once the car is warm it drops to about 20-25lbs at idle. I was wondering if I should use a thicker oil such as 10w-30 or even thicker. The engine is a 69 sbc 350 with a 471 blower on it. The car seams to run at a good temp around 180. I won't be driving the car in cold weather so that won't be a factor either. I even installed another guage on the block to do a comparison and they run about the same. any advice would be appreciated thanks.