Actually, we refer to you folks in Southern Ontario as being "down south" so quit whining about a minor cold snap.
![[Razz]](images/icons/tongue.gif)
Just kidding!
Was -42 F last week and is now a balmy 4 F / -16 C. Once it gets colder than -40, F and C have little meaning around here!
I would wonder if the GC thickens quite a bit with extended use? Does your car make any nasty noises once started?
I covered this in another post, but here we go again:
According to the SAE J300 test, the "borderline pumping temperature" is the "yield stress" when the oil is >60,000 cP. The BPT simulates oil flow from the oil pickup tube to the oil pump, and is the MRV BPT (Mini Rotary Viscometer Borderline Pumping Temp).
Also according to my Esso Lubricant Products Handbook, the following grades are listed to their absolute lowest ambient temperature use:
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 oils. Every oil from every maker will test differently on the MRV BPT.
For example, Mobil sells a synthetic 0W-30 in Europe that turns solid at -38 C, so different markets have different priorities.
I worry about cold temp performance as I ordered new a 200 GMC Sierra with Vortec 5.3. It has a rear sump oil pan, the oil pump at the very front of the crank, and a very long oil pickup tube.
When new, with the factory-fill "low bidder" 5W-30, it made knocking sounds at temps colder than -10 F, and oil pressure took about 10-15 secs to build up.
With Mobil 1 0W-30, between the time I turn the key to start, it starts instantly, and when I glance at the gauge it's already up. No noises at all, even at -42 F.
I run Mobil 1 0W-30 in winter and Mobil 1 10W-30 in summer. The 0W-30 has a MRV BPT of -58 F, so no problems even at -42 F.
I've seen cars around here break the oil pump drive when boosted at -42 F.