Originally Posted By: ammolab
It is when those engineers "spec" OW-20 Oil in the US manual. Then they spec 5W-40 In the Aussie manual and I loose all confidence in them, or 20W oils, or something.... I AM SO CONFUSED!
Well, sometimes, perhaps, it's the marketing people causing confusion, not the engineers. Just because the Australian or European divisions of a manufacturer specify a 40 weight there, while the North American divisions (and even Japanese divisions) specify a 20 weight doesn't mean that the 20 weight is the wrong choice.
Look at it this way. Why do we have 20 weights specified in Canada for the same engines that are so speced in the United States? It's not because we have cold winters. It's not because of CAFE, since that's an American regulatory regime. It's probably because it's convenient. It's quite likely because oil companies' product lines are very, very similar across the United States and Canada. The API/ILSAC system is well entrenched in both countries, too. Even logistically speaking, it makes sense for the manufacturers. Cars made in the States stay there and go to Canada, and the same applies with cars made here. One factory fill, one service recommendation. Then, there's one less thing to tweak in owner's manuals and service manuals.
The diversity in climate may even play a role, too. You know darn well that if a manufacturer allowed for a 20w-50 under appropriate weather conditions (i.e. Texas in the summer), someone is going to run 20w-50 in a Saskatchewan winter, and then grumble at the manufacturer after they spin their bearings. Also, in North America, if 5w-40 was the preferred grade for every vehicle, we're going to have people (including me) balk at the price of synthetic for an application that really doesn't require it. So, the manufacturer could extend the OCI, then someone who doesn't like synthetic prices runs 10w-40 dino for way too long.
It's also kind of hard to go for an extended drain if one has to switch viscosities across the seasons.
