Recently we've seen a trend on here that in the cold weather the iron numbers go up in UOAs. I know we've mentioned corrosion as a possible reason (colder weather=more moisture I assume) but is it possible that with extreme cold that the higher iron is simply the fact that the engine is under so much more stress on a cold start since the oil is so thick and cannot offer as good protection? This trend disturbs me so much that I have totally revised my oil change schedule for all the cars I change oil for (4 of them). From now on I will always change the oil in April, when the cold weather is mostly gone, instead of trying to push it further. I think the oil will have taken such a huge beating over the winter months that it's not worth it to run it longer. This might mean in some situations (such as with my mom and wife's car) that I might be draining out the oil before 3k! As much as I'd hate to be changing oil sooner than this mark, I also want to do the best for these engines and I just feel the winter takes too much of a beating on the oil.