Non totally optimum performance is not really a problem. The real problem is that USA is huge and cover many different climates. If you drove a car from Florida

Non totally optimum performance is not really a problem. The real problem is that USA is huge and cover many different climates. If you drove a car from Florida to NY without taking this in mind, in theory you could end with a non working car stuck in the middle of a dangerous blizzard I think that there is even a -5W grade for people in really extreme climates like Canada, Russia or Alaska, but I never had seen it. Maybe somebody here uses it? The last number in oil grades will be 20, 30 or 40 typically for cars. 20 will lubricate pieces faster.