dustyroads
Thread starter
Originally Posted By: Shannow
dustyroads,
your temperatures should be fine.
Here's a couple of charts that I've lifted from some older studies, but should help explain what you saw...your engine will be different, and behave differently, but the trend is there.
Two measures are used in the "W" rating of your oil, yours being 10W. MRV and CCS.
MRV is how the oil flows under low shear rates, in feeding the pickup screen, and flowing into the pump to be pushed around. CCS is how the engine cranks.
Here's an idea of what the "W" rating does to the startability of an engine...the CCS moves the "startable" point, which is the engine turning over quick enough to fire to the cold end.
Here's what the MRV does, and this particular test on two oils shows that the establishment of oil pressure depends on how well the oil makes it to the pump to be pushed into the oil galleries (much smaller extent on how it flows THROUGH the galleries).
Same thing, lower "W" moves the behaviours to the colder ranges... RAOT is how long oil took to flow from the rockers (on that engine), and FOPT is the time to full oil pressure.
In the starts that you describe, there would be little to no change in your 4 seconds by going to a 5W or 0W...drop another 10F, and the 10W might take another 10-15 seconds to do the same, and a 5W would be in it's realm.
Thanks Shannow. I knew about the cold crank numbers (in the most elementary way) hadn't thought about the MRV numbers and just how they pertained to cold flow. Very cool seeing those times for each oil.
I have tried a dozen times to download the PDF for Delo SD 15W30 but it fails each time. I wanted to see how that compares to a 10W30 in the CCS. Maybe it wouldn't say, anyway. I know being a 15W it wouldn't compare favorably to 10W30 but as a 30 grade I'm curious as to how it looks vs a 15W40 in cold testing.
Thanks again for the info. I will use -26 or so as my cutoff. Anything colder, I will figure on idling (with 10W30).
dustyroads,
your temperatures should be fine.
Here's a couple of charts that I've lifted from some older studies, but should help explain what you saw...your engine will be different, and behave differently, but the trend is there.
Two measures are used in the "W" rating of your oil, yours being 10W. MRV and CCS.
MRV is how the oil flows under low shear rates, in feeding the pickup screen, and flowing into the pump to be pushed around. CCS is how the engine cranks.
Here's an idea of what the "W" rating does to the startability of an engine...the CCS moves the "startable" point, which is the engine turning over quick enough to fire to the cold end.
Here's what the MRV does, and this particular test on two oils shows that the establishment of oil pressure depends on how well the oil makes it to the pump to be pushed into the oil galleries (much smaller extent on how it flows THROUGH the galleries).
Same thing, lower "W" moves the behaviours to the colder ranges... RAOT is how long oil took to flow from the rockers (on that engine), and FOPT is the time to full oil pressure.
In the starts that you describe, there would be little to no change in your 4 seconds by going to a 5W or 0W...drop another 10F, and the 10W might take another 10-15 seconds to do the same, and a 5W would be in it's realm.
Thanks Shannow. I knew about the cold crank numbers (in the most elementary way) hadn't thought about the MRV numbers and just how they pertained to cold flow. Very cool seeing those times for each oil.
I have tried a dozen times to download the PDF for Delo SD 15W30 but it fails each time. I wanted to see how that compares to a 10W30 in the CCS. Maybe it wouldn't say, anyway. I know being a 15W it wouldn't compare favorably to 10W30 but as a 30 grade I'm curious as to how it looks vs a 15W40 in cold testing.
Thanks again for the info. I will use -26 or so as my cutoff. Anything colder, I will figure on idling (with 10W30).