That is interesting. What you are saying is Forte encourage garages to supply & charge for goods not asked for, knowing that most people will pay. Is that the sort of business practice any of us wish to be associated with?
I have no personal gripe with Forte, their products may well be top notch, but I don't feel this is right. I know some of the main dealers in my area do use these or similar additives in the way described above. Thier customers may not complain directly to them, but some have mentioned to me that it is one reason I now get the business instead.
Don't most manufacturers invalidate warranty if additives are used?