Same grade with differing low start temps

[mjoekingz28]

I am just thinking right now and can remember SOME instances of this, but have no charts or evidence....so if anyone can post anytbing then that would be excellent.

Why is it that a SAE30 will pump down to zero degrees in some cars and some others the chart in the manual might say to use never below 50 degrees.

Like in a motorcycle a 20w-50 is the year round oil, but in a car you better not go below 40 degrees.

Or an OTR diesel that can drive the entire 48 states on 15w-40.


Is it a stronger oil pump or maybe bigger galleys/galleries for the oil to flow through.


Again. I am to not post falsehoods but I intend to clarify. So forgive if the examples are wrong.

 

[SilverFusion2010]

Good question. I assume there is something designed differently for each of your examples. I’m not an expert in engine design, but I suspect it’s more that the motorcycle Needs the 20w-50 regardless of ambient temp, and has less mass to spin on start. The oil passages would be shorter and the engine overall smaller vs the car or the diesel semi. Basically a motorcycle engine is easier to spin so more oil drag can be tolerated is my theory. Diesels are high compression and need big starters or compressed air start, plus I think most of them have block heaters?
The car lands in the middle

 

[Shannow]

There's a series of papers on cold temperature starting that show quite a marked change in startability and oil pressure rise due to different engine designs.

The Jeep 4.0 is about the worst.

OVERKILL shared some pics with us before, maybe he'll find the thread and hook us up.

 

[gfh77665]

Originally Posted By: mjoekingz28

Why is it that a SAE30 will pump down to zero degrees in some cars and some others the chart in the manual might say to use never below 50 degrees.


Technically, 30wt probably would pump at 0. For best results though, using 30wt above 50 degrees would be best. The difference is what is "possible" and what is "optimal". You just have to keep information in context.

 

[barryh]

Originally Posted By: mjoekingz28


...Like in a motorcycle a 20w-50 is the year round oil, but in a car you better not go below 40 degrees...

Is it a stronger oil pump or maybe bigger galleys/galleries for the oil to flow through.


It's supposed to be due to larger bearing clearances but what happens when you put 20W50 in my 79 BMW motorcycle is slow winter cranking and when it does start stupidly high cold oil pressures. 20W50 is just inappropriate in 2018 except in warmer climates. I use a 5W/x oil The 50 part can still be relevant especially for air cooled engines as in some cases they run very high oil temperatures