[Lil bastard]

Personally, I wouldn't use it. It's primary ingredient is Petroleum Distillate JP5 (Jet Fuel 5) which is essentially massaged Kerosene.

It wouldn't do any harm, but not a lot of bang for the buck, unless the parts are soaked in kerosene for a period of time, there are better, faster acting solvents out there.

Whether or not you actually need it depends on your driving style, frequency, brand of fuel used, etc. Spending the same money on extra fuel and taking her out for a run will probably accomplish the same thing, with the added enjoyment of seat time.

The gas today is really good and unless you store the car or drive VERY infrequently (fill-ups only every 6-mos.) you really don't need it. I don't add a thing to any of our daily drivers because the fuel itself with all it's additives, does the job.

My car gets stored every winter - long enough for varnishes to form from the gas and potentially clog injectors, so every spring, I add a can of Lubromoly Jectron which targets the injectoprs specifically but also dissolves varnish. For valves, I would choose Lobro-moly Sauber. I think together they're cheaper than the Gumout and probably more effective.

Lots of people swear by lots of these products, but very few are really effective and many are just repackaged, and up-priced, common chemicals.