I've only used it about 10 days (when I installed a different steering gear - old one was previously adjusted too tight) but I know of others who have been doing it for a long time with no problems & excellent cold weather performance. I've been using Mobil 1 synthetic ATF in my tranny for 67,000 miles and have no problems. In cold weather the first shift is as smooth as if the car has been running for 12 hours or its 90F outside. I ran the Febi-Bilstein "MB" PS fluid (from Fastlane) for about 55,000 miles with no problems either, but not in cold weather. At $6-7/qt for the Febi, MY opinion is that I don't think its cost effective when Mobil 1 ATF is cheaper.