Originally Posted By: bbhero
I agree to a point. One aspect of this pour test that does correlate to the real world is that Castrol is a bit thicker at cold temps than some other oils. This pour test does verify this phenomenon rather well. Question I have is what MRV is so high that a car/truck wouldn't be able to start??
Well, it's one data point, and it really doesn't tell us a whole lot. That's one reason VI exists as a measure, too, because two equal grades at KV100 might not be so equal at KV40. And, some oils truly do have pour points that suck. There's no doubt about it. But, pouring and pumping are not the same.
With respect to having an oil with an inappropriate MRV, well, a couple things can happen. Normally, if the oil is simply too thick, you simply won't be able to turn over the vehicle fast enough to start it. Sometimes, that's a good thing. Back in the days when carbs were more prevalent, you could fairly easily get a vehicle to start when it certainly wasn't in its best interest. When I was young, a buddy and I picked up a Duster to sell off. It had 10w30 in the sump, and had no problem starting unaided in -40. 10w30 is certainly overmatched by -40, particularly unaided. It started, but I doubt I was doing it any favours.
With a fair number of fuel injected cars over the years, I've found that if you're running something that's more appropriate as a summer weight, when it hits those ridiculously cold temperatures, it won't turn over fast enough to catch. With a vehicle with a carb, at least on every vehicle with a carb I've owned, if the battery is decent, and you do things "right", it's going to start, even when you probably shouldn't do so.
The Imperial Oil Esso video on YouTube about 0w30 gives a good example of using an improper winter viscosity oil versus using a proper winter viscosity oil, in what we'd call actual cold cranking temperatures.
Yes, they use the pour point demonstration. And no, this doesn't mean you need a 0w30 in 20 F. Look at the five minute part, to watch the start. Also, look at after the eight minute part, to see an appropriate oil being pumped, and an inappropriate oil being pumped. You want the oil to be able to be pumped in the temperatures you're facing when you start your vehicle. Right now, it's -3 C here. 15w40 will work fine. When it gets to -35 C to -40, a 5w-XX or better is my choice. And, I can run it all year, too.
