When I first got my Bronco in 05 the oil pressure was 20 psi at idle and 50 psi at 55 mph with 110K miles(with a mech.gauge set).Now with 140K and with the last 13K miles travaling fully loaded at 4200 lbs. the pressure is still 20 psi at idle but 39 psi at 55 mph with 10/30 Mobil 1 full syn.high mileage oil.Would using heaver straight weight oil be a better choice to increase the oil pressure?
