I think of lot of guys use this for the smoke show it produces out the tail pipe.Pay no attention to most of the Youtube videos you see about this product:almost all of those people are using it wrong.WRONG WAY: start car, pour seafoam into fuel, oil and PCV valve or carburetor (or similarentry point to the cylinders) and then stamp on the gas hard until it looks likesomeone detonated a hydrogen bomb in your neighborhood.RIGHT (and more mature & informed) WAY: start car, let it warm, pour in Seafoam tofuel, oil and cylinders.  Once all used, TURN OFF CAR.  Let sit for at least 5 minutes(preferably 15) and then turn the car back on and DRIVE IT somewhere, aggressivelybut not irresponsibly.  Do so for 20 minutes or so or at least until the smoke dissipates.Most cars don't need this treatment but I can see it on an older car or a vehicle that'sbeen abused and requires a full tune-up.Be ever mindful that the deposits you liberate from the engine may, in fact, be all thatholds the motor together.  Oil might not lubricate as well (or at all) if the clearances betweenbearings are so wide (without the deposits in place) that it can't reach them.  Take care whenusing this product, and do so responsibly.Better idea: run 20% Marvel Mystery oil in your crankcase (use 1 of each 5 quarts as MMO), add 4 or 5ounces of it (per 10 gallons) to the fuel, and pour some down the carburetor (or into PCV valve or acarefully-selected vacuum line) ) once the car is started.  Don't go crazy with the amount you pour intothe engine directly.  Run it in a new oil change: use cheap (but new) oil.  Use a cheap (but decent)  oilfilter like a Fram ExtraGuard [the Orange Can].  Run for 2-4 weeks.  Change oil again with a good filter(Motorcraft are my favorites but Purolator and Mobil 1 are great as well) and decent oil (preferably synthetic)and watch the crap drain out with the oil/Marvel Mystery Oil combo.  Continue to run good oils and filtersfrom then on, and perhaps repeat this procedure every few years or as you believe it necessary.Seafoam is a far more aggressive crankcase cleaner (flush) solution which fewer cars are inbad enough condition to require.  But for those that are, it works well.  Just use correctly andresponsibly.  And beware that it may clean out exactly what was holding the motor together all thoseyears.  Still, few vehicles will have that problem.