Penz 5W-30, 10W-30 and GTX 5W-30 in Canadian winters

[Rick]

I have 3 friends that use both pennzoil and castrol gtx all winter long. It can get **** cold outside here. The question is, are they killing there engines faster by using these oils in the dead of canadian winters?

 

[JonS]

I don't think they are killing their engines. I use Pennzoil 5w-30 in our winters at -25f. I have had no problems. If you have a good battery, dino 5w-30 is good down to -30f.

 

[Rick]

But what happens when the temp goes down to -35?

 

[geeeman]

Nothing...cause you stay inside!!!

 

[Rick]

I was kinda looking for a serious answer here.

 

[Patman]

If the temperature is consistently getting down to -35C in your area, you need to convince your friends to start plugging in their block heaters overnight, or switching to synthetic 5w30 or 0w30. I for sure would not want to be running a dino 10w30 in those kinds of temps. They are most certainly reducing their engine life significantly with each -35 degree start they make (assuming their car is parked outside overnight, if it's inside the garage it's a different story)