Re: Engine oil

Posted by Fish'n Jim On 2015/6/28 11:33:18

Another way to think about it is based on rpms. Each stroke or turn of the pump is producing a shot of oil. The faster the motor turns the more you need lubricant to the rotating and stroking parts and the more the pump delivers. eg; oil flows out on the cylinder wall on the up stroke and is wiped off in the down.
The gauge pressure is only showing the resistance to flow that's encountered, not the flow. Flow's pretty much fixed by the pump capacity. There's more resistance to flow the higher the flow in the same size channel. So gauge pressure will noramlly increase with rpms for these mechanical pumps up to a point.
No need to modify the viscosity. In fact, you might starve the pump inlet/pickup at lower temperatures with higher vis.
Diesels are a higher temperature and pressure animal producing more combustion soot/ash than a low compression '40's gasoline motor. So diesel lube requirements are much different and more severe. Use diesel grades for diesel service and gasoline grades for gasoline motors.
Your motor probably spec'ed out for ND 30W with leaded gas and some have filters and some don't. That was pretty much the most available refined motor oil grade at that time. The economics were to dump the contaminated oil frequently rather than make it last. Not same economics as we have today.
If you look at motor oil viscosity curves, you won't see as large a change in viscosity with temperature as the "W" numbering system suggests. In fact, they all get much thinner at operating temperature well below what you pour out the can.
I won't get into additives. I've addressed that one before.