D310 oil pressure in General IH Posted July 21, 2020 I recently rebuilt a D310 and installed a new oil pump. I’m running 15w40 oil. On startup my oil pressure spikes to about 90psi and after it warms up it drops to 50. If I really work her hard it’ll drop down to 30 at idle. Outside temperature is 80 degrees. is this normal? I’m using a $80 auto meter mechanical gauge. I haven’t checked any other gauges. The oil pressure gauge and light take about 3 seconds after startup to begin reading pressure.