Borderline pumping temperature

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Staff member
May 27, 2002
Guelph, Ontario
The one thing I have noticed on spec sheets that list a borderline pumping temperature is that it is exactly 20F difference than the pour point. And since Schaeffers doesn't list a pour point for #703, but does list a BPT of -40F, that must mean it's pour point is -60F! Cool! (or should I say COLD!) [Big Grin]
Everything I have read says the pour point is 20F lower than the pump point, by definition. The pump point is the minimum temp that matters if your concern is cold weather operation. Here in NC I am usually not too concerned with extreme cold like some of y'all up nawth!! he he Good mornin everybody Rando
Despite what people think about Canada being the Great White North, it's not really that cold here in the Toronto area in the winter. It rarely goes below 0F. Most overnight winter temps are closer to about 15 to 20F actually, and daytime highs are usually around 30F. But it's nice to have an oil with a -60F pour point nonetheless.
Patman's sniffing the oil oil oil oil again. [Big Grin] [freaknout] It wouldn't suprise me to see a low a pour point if it has 25-35% PAO. Speaking of PAO [Off Topic!] I put 60ml of 20W20 non-detergent mineral oil (SA) in a bottle and placed a few drops of it on the end of a 1/2" shaft (4140 tool steel) and started to drill some holes in an axle shaft in order to place cotter pins to secure two wheels. The mineral oil smoked like crazy and the drill (new) barely made a dent. Drill and shaft were blistering hot to the touch. I then added 5 ml of PAO and 0.5 ml of TMP ester to the mineral oil. I washed off the bare mineral oil with solvents. I placed my newly formulated mixture on the shaft and drilled with another new drill. There was no smoke whatsoever and the metal filings came out of the hole in long strings, while the drill went through the shaft like cheese. Both drill and shaft were cool to the touch. As soon as my Schaeffer's arrive, I will try the same experiement with their mineral/PAO/Moly blend and report what happens. borderline pumping temperature is just that...borderline. So, say I am looking at an oil with a -39F pour point. That would give me a BPT of around -19F. What is the lowest temperature that I should feel comfortable using said oil? Do you put another 10F or 15F on top of that and say -5F is good? Then, viscosity still comes into play here doesn't it. last week I took Delo 15w40 and Valvoline 10w30 and put them in the freezer for 2 days at 8F. Delo has a -39F pour point, Valvoilne has a -27F pour point. I took 6oz of each (still at 8F and ran them through bottles with about a 3/16 orifice drilled in the lid. The Valvoline took 1 minute. The Delo took 1 minute 45 seconds. I know that this was far from exact science, but it still told me that oils with similar pour points but different viscosities act quite different. opinions? thanks, Matt [ September 02, 2002, 05:52 PM: Message edited by: matt cook ]
Matt, I'd say that 10F above the BPT would be a good low temp limit to use. The engine will turn over down to the BPT of the oil, but it may turn over very slowly and you won't be getting great lubrication. A 0w-30 or 5w-30 will outperform a 10w-30 or 15w-40 in cold weather, regardless of who makes the stuff. TooSlick
I know that this was far from exact science, but it still told me that oils with similar pour points but different viscosities act quite different. opinions?
What you did was a simple viscosity test. Visosity is resistance to flow. You were seeing how they flowed. A higher vis oil will take longer to flow than a low vis one. Just before they freeze they will both stop flowing. If the BPTs are the same, the higher vis oil will still flow slower than the low vis one, until they stop flowing.
Is "borderline pumping temperature" the same thing as "pumpability limit"? If so, Patman's rule-of-thumb doesn't hold true for the Mobil1 spec sheet I'm looking at.
I think that is a different spec alltogether. This is where things get confusing in reading the oil specs!
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