they are recommending 5w-30 (not 10w-30).
Yes, my bad. That is what I saw too.
From what I see, this letter clearly links 5W20 to CAFE gas mileage, but I don't see anything that implies lack of lubrication.
TSB Patriot Europe
This one is the most persuasive. The problem is there is no explanation why the change. As some had said, they thought it had to do with the speeds on the autobahn.
Machinery Lubrication Article
There are many articles like this on the internet. Some of them are copy and pasted word for word. They make perfect sense but are a little inconclusive. Their bottom line is...
The best oil for your vehicle depends on your driving habits, the age of your engine and the climate you drive in, but it is not necessarily the type of oil specified in the owner’s manual or stamped on the dipstick.
So, if you tow something or spend most of your time on the highway in 100 degree temps, you should probably go with a heavier oil. If you are driving around town with 10 degree temps, you should go with a lighter oil.
You know what, I'm probably making too big a deal about this. Maybe I should go with the 5W20 in the winter and 5W30 in the summer.
Some people have stated that with our lifetime warrentees, if the engine has problems we'll just get new ones. Well that's not quite the way it works. When something goes wrong, they will fix what is wrong and nothing else. If one rod bearing spins, they will replace that and probably nothing else and they'll hope you get sick and tired of messing with it rather that bring it back again. That's just the way it is. Any work they do for free is going to be minimal.
That being said, maybe I'll just go with the 5W30 all year.