The cap on my power steering reservior as well as my owners manual reads ATF only. I recently had a leak in my system during which the power steering fluid res emptied out and the steering became almost impossible. I was only a few miles from my mechanic so I drove the car straight there (only one turn the whole way). After repair of the leak my mechanic used 11S to refill (he did not do a complete system flush). Will this harm the system or is it better as he claims? I swear that the steering now feels slugish. BTW the car is a 1996 740i.