when i started driving you would ALL WAYS check oil pressure be fore buying a car. my dad said the most important thing was that as the rpm goes up the pressure should go with it. fast forward 2012. my 2001 dakota with a V-6, auto trans, mostly stock, 4.1 rear gear. valvoline premium blue 15w-40 and red line break-in additive. driving a road got up to 70 mph for 3/4 of a mile, air temp 90 F. engine temp stayed very good. at the next stop the oil dropped to the mark before the bottom. as i took off the oil pressure came right up. the Q is , am i ok?

 

Put a mechanical gauge on it and read the pressures. Your sending unit may be going out if it reads that low.

The pressure going up as you drive is normal operation.

 

Why 15w40?

 

15w-40 some of the chrysler factory service said to use oil as thick as you can use and still start it in the winter. my self i all was wanted the oil to stay between the bearings, i think this can be done with thick oil. and YES it has bit me in the but. and i do want to go to a mech gauge.

 

5w-30 is spec'd up to 100 degrees, 10w-30 above that.

Going thicker can starve the bearings of oil as the clearances in a modern engine are tighter than those of a few years ago.

 

yes i know every one is going to thinner oil. i just have trouble with that. my 2001 3.9 calls out journal clearance at.001 to .003 in. my 1967 dodge factory service manual calls out on a 318 crank diametral clearance .0005-.0015. just for a reff.