The CFSC (complete fuel system cleaner, or SL-1) is supposed to be safe to use continuously, and I think BMW endorses it. My car was running great right before and after I had my 30K/2 year service. I had used Techron concentrate before my service, but now the car seems less peppy once again, the fuel MPG is back down and I sometimes get a slightly rough idle. I run a lot of short trips, and think I might be having carbon buildup problems (the 5 valve turbo and oxgenated gasoline contribute to this, from what I have read). I want to try running some of the Redline CFSC for a few tanks (maybe even on a ongoing basis) since continual use of Techron is not recommended. As a note, the last few tanks of gas I have used were Mobil and Exxon instead of the usual Chevron, and it has been much warmer/humid here in Dallas lately.<p>Dave M - '97 1.8tm