I lost about 8 psi of
oil pressure when I added an
oil cooler to my road racer, small block Ford engine... I have used 4 different
oil coolers over the years (headered type and single pass type) and get about the same results with all four... also using 12 AN lines... Talking to others about this, I think a 5 to 10 psi loss with an external oil cooler seems about the norm...........
David