When I use it, I will put a full bottle in the gas tank (full of gas of course), depending on my oil, if it is a little below full, I will put a full bottle in the crankcase (run it for a few days then change the oil!), and I put a full bottle through the brake booster vacuum line. (I iuse a funnel in the end of the hose and pour a little in at a time) When you put it through the vauum line, just pour enough at a time to let it bog (don't let it die), and keep doing until an amount is left in the bottle to let it die with that amount being poured in. Let the car sit for about 5 or 10 minutes (to let the Seafoam soak in), and then start it up and drive it around (if you have a safe area to do so); if not let it sit where it's parked (but not inside a garage) and you will be amazed at the smoke,a result of the carbon and gunk being burnt out.
Great stuff, Seafoam is. I use it in a car about twice a year.
$9.99 a bottle x3 for each car, but I have felt the difference in the car running better, smoother.