i use 15w-40 & at about 70~80 deg C oil temp, i get very low pressure readings -- some times as low as 0.2bar at 800 revs of idle. in my case, what could the problem be..? i've suspected my turbo and my crank seal which leak slightly but these are all on the low-pressure side of the circuit and i doubt they would have anything to do with the pressurized side of the oil circuit.. :/