so i bought some forte topend treatment, and it doesnt have any instructions on use, now i know you add it to your oil but... are you meant to remove 400ml of oil to pour 400ml of the forte in, or do you simply add it without removing any.

Overfilling the oil is wasteful and can cause problems, so if I was going to use that stuff (which I never would,) I would drain 400 ml. first.

DONT  GET ON  YOUR  PAINT    BUD     I USE  SLIK 50   FOR 40 YEAR NOW    

Hi you are supposed to put it in as a substitution for 400ml of oil when you do your oil change, using fresh oil will give the best benefit of the product, I like Kev have used Slick 50 for years and obtained spectacular milage from all of my cabs, 247k, 310k, 270k, with minimal engine wear internaly so from my perspective these thing work as they are basically a friction reducer, you will always get the element who think all of these products are Snake Oil but in my opinion how can you knock something if you have never tried it and have no idea what it does, I think the question was, having decided to use the Forte do you add it as an extra or take out 400ml first to accommodate the additive, I hope I have answered your question.

Regards Steve.