24-01-17, 03:41 PM
Aftermarket additives often seem to generate an almost religious faith, typified by the sort of abusive over-reaction you get when you suggest some scientific evidence would be useful.
I haven't tried any of these treatments, regarding them as a complete rip-off. Added to which, I'd be very reluctant to use anything containing solvents such as xylene or trimethylbenzene as they're damaging to most types of rubber.
There's never been anything in my carbs by way of varnish deposits that these overpriced paraffin/detergent/paint thinner mixtures would be able to shift. The only time they have have suffered blocked jets it's been with inorganic metal salts and hydroxides caused by bimetallic corrosion... physical cleaning has been the solution.
I'd agree with the Pieman, the occasional tankful of high-detergent fuel is probably a more economical way of dealing with any varnish. And a long hard thrash is a more effective (and enjoyable) way of burning off any carbon deposits caused by a lot of short, slow journeys... it also has the side-effect of turning any mayonnaise in the sump back into oil.