Shell is .89 a liter here in Edmonton, -for the good stuff. Government says in premium gas they must put 'x' amount of cleaners in it. That's what most probably do.
Shell states they put 5 times what is required by law. On their web page they took an old clunker and fed half the motor with their gas and half with everyday corner stuff. Of course one half of the motor got quite clean after a few tank fulls.
Anyway you have years of carbon build up... top of the piston, valves, etc. Unless your motor is shot, stuff put in the crank case isn't going to make it past the rings to get in the cumbustion chamber. Here is a link to the 'v-power' site...
http://www.shell.com/home/Framework?...t_ga_1602.html
hope it works or you could cut and paste it in a tab