I've been told by several sources to stay clear of Lucas products (their specifications come nowhere near the products I use). If you use a top quality engine oil or tranny fluid for example (in my case, both Amsoil synthetic) there should be no need for any additional 'additives'.
As for the fuel system.....using high quality gasoline should be sufficient along with proper maintenance. Once a year (on a long drive) I will use a bottle of Redline fuel system cleaner, and that's it.