It doesn't sound like you're hitting the limit of a regular 10W-30 at your temps.
I have a hard time finding test specs so I'll quote the Esso products, since they appear willing to publish all the data.
For some reason Mobil has stopped publishing detailed test specs. Maybe they have something to hide?? Anyway, I saved the Mobil HTML from Feb 22 of 2003, and they still listed SuperSyn specs.
Esso Protec Extra, something you'd probably find at a Wally World or a service station in Canada, has the following test specs:
CCS viscosity at -25 C:
Esso Protec 10W-30 6,490 Poise
Esso Protec 5W-30 3,000 Poise
Mobil 1 SS 10W-30 3,848 Poise
Mobil 1 SS 5W-30 3,600
note: M1 5W-30 at -30 C for CCS
MRV viscosity at -35 C:
Esso Protec 10W-30 60,900 cP
Esso Protec 5W-30 25,000 cP
Mobil 1 SS 5W-30 12,700 cP
MRV BPT:
Esso Protec 10W-30 -35 C
Esso Protec 5W-30 -39 C
Mobil 1 SS 10W-30 -41 C
Mobil 1 SS 5W-30 -46 C
It sounds like you have a mechanical issue if there are knocking noises at +20 F
Jerry