Whenever I get a new (old) car, or work on a mate's, or am pulling something out of storage or tuning, first thing I do is dump a bit of seafoam in the oil, a bit in the tank, and a bit into the intake (methods vary, usually through brake booster line into the intake manifold), and watch the big brown cloud of crap that comes out.
If I do it to a car or something I've already done, the cloud is the typical blue smoke cloud that looks like you're burning a little oil.
Just right after a few complete heat cycles (a few 'spirited' drives and back for cars), I change the oil and use up as much fuel in the tank as I can until I can just barely make it to the petrol station. Not until I get some new gas in there do they stop smoking completely, though at that point it's just usually a teensy puff every stop sign and again).
Does wonders for cars, weed whackers, and motorbikes. Also use it to flush out bad carbs.
The specific brand isn't too important (just a mishmash of certain hydrocarbons), but habit and laziness makes it easy to grab the same bottle every time. Also stabilizes fuel a bit, too; though do change the fuel filter if you run it to an almost empty tank with Seafoam - usually clogged by then.