Part Two: Cleaning Your Oil System
as you all should know, f-bodies require 5.5 quarts of oil. seafoam is to be added directly into your crankcase in order to cleanse the oil. yes, you heard me, you're pouring a foreign mixture directly into your engine oil. this can be scary for newbies. never fear, seafoam is 100% petroleum. it is as harmful to your engine as water is to your skin - not harmful at all. the correct measurement for seafoam is 1.5 ounces per quart of oil in your crankcrase. simple math tells us:
(1.5) X (5.5) = 8.25 ounces
a can of seafoam is 16 ounces, so for simplicity's sake, we'll add half a can directly into the ENGINE OIL spout. NOTE: i recommend pouring the seafoam into your oil when the car is cold. i would not recommend pouring a room temperature liquid into 200+ degree oil after the car is hot. last thing you wanna do is shock your valve springs.
run the seafoam in your oil for NO MORE THAN 250 miles! seafoam is very agressive. your next oil change will be black as satan's heart and likely thicker than usual. i would not recommend running this oil very long in the car as your oil filter is going to have quite the time on its hands and the oil won't be in the best of shape afterwards. i'll say it again. change your oil less than 250 miles after you put seafoam in your crankcase! i personally recommend running it 100 miles, then changing your oil. that should be plenty for the seafoam to get most of the gunk out.
got that from the Full Size Chevy forums... Hope that helps