I've been using it for years. Not a problem. It has solved problems. 1996 Windstar van - slipping, 1 bottle of Lucas, no more slipping. Friend had a 2001 Odyssey - MIL/CEL transmission service required. Dealer said - new transmission $4500! 1 bottle of Lucas, 20,000 miles later, no MIL/CEL, no slipping, and $4490 ahead of the game ($10 for the Lucas). 1998 Ford Contour, slipping out of drive at idle, fluid brown, smelling burnt. Transmission drain, flush, and 1 bottle of Lucas - now crisp smooth shifts, no more dropping out of gear. 1997 Lincoln Town Car, noisy steering pump. Flushed steering fluid, added 8 oz Lucas, nice and quiet now a days. Same Lincoln, transmission fluid change/flush 1 bottle of Lucas, fuel economy went from 18 MPG to over 19 MPG.
Not sure what is in that stuff, but I've not had a single failure related to it, yet it always seems to fix any failure that I throw at it.