fuel additives professing to clean the injectors...do they work?

i always buy a lubricant/cleaner at the esso truck stop on barlow and peigan (s.e) corner. not the shell. There is one there that has mostly french labeling that sells for around 13 dollars. I think it treats around 3000 litres. I always double the reccomended dose and my ailing old injection pump has survived an extra 75000 klicks from using a lubricant. The one i mentioned seems to work as good as good as stanedyne