Straight from their website
DIRECTIONS
For regular fuel system maintenance, add 1 ounce per gallon.
For cleaning, use 2 or more ounces per gallon – the more you add to fuel, the better it cleans! Add when the tank is low to maximize cleaning concentration.
For injector cleaning machines, use 50/50 mixed with gas.
Use 100% Sea Foam for diesel injector cleaning machines or when priming diesel fuel filters.
For 2-stroke pre-mix, add 2 ounces per gallon.
When stabilizing fuel for storage, use 1 (one) ounce per gallon of fuel. Sea Foam works to stabilize stored fuel up to 2 years.