Oil grades and pressure delay on cold start

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Oct 22, 2003
By Detroit
Yesterday I started my truck with 10w40 after it had sat for 9 hours in 10F temp. I counted 3 seconds before the mechanical pressure gauge needle moved off zero. Maybe that is how long it took to build enough pressure to open the oil filter bypass valve. Anyway im curious how it goes for others with different oils. May be complicated because my pressure line fits beside oil filter, but on another vehicle it is at the opposite end of the engine and higher up and thus has a couple second delay even in warm weather. Anyway, if you have a real gauge list the temp, how long it sat, oil grade, oil brand/type, and seconds (counting one-one-thousand, two-one-thousand, ... OR by a clock), and any other possibly related info. This won't be scientific, but maybe we will learn something.
5w-30 in -8 degree weather in my Dad's 4.3L Blazer takes about 2 to 3 seconds to be at full pressure. And that's with the factory remote filter mount which I'm sure increases the time of full pressure as the oil has to travel about 3 times as far to get to the sending unit. It probably doesn't drain back to the pan as easy though [I dont know]
I put this in a different post, but here goes: The SAE has determined that a "yield stress" of > 60,000 cP will cause oil to stop flowing at the oil pump. So you will have a dry start and possibly not have oil flow at all. This is part of the SAE J300 "borderline pumping temperature" recommendations. Most oil companies test using the "MRV BPT" (Mini Rotary Viscometer Borderline Pumping Temp)which simulates oil flow from the oil pickup tube to the oil pump. My Esso Lubricants Product Manual has the following caution about "expected ambient low temperature" and at what absolute lowest temp a given grade of oil should be used: 15W-40 -20 C (-4 F) 10W-30 -25 C (-13 F) 5W-30 -30 C (-22 F) 0W-30 -40 C 0W-40 -40 C The "0W" oils are partial synthetic HD diesel engine oils. The engine design has a big influence too, which us why I have always been concerned about my 2000 GMC Sierra with Vortec 5.3 that I ordered new. It has a rear sump oil pan, an oil pump mounted to the very front of the crank, and a very long oil pickup tube. With the factory-fill "low bidder" 5W-30, it made knocking sounds at -10 F. I switched to Mobil 1 0W-30 for winter and it has never knocked, even at -42 F: a BPT of -58 F helps here. Its HTHS is a little too thin IMHO. I've seen cars around here break the oil pump drive getting a boost at -42 F.
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