In my case I used Gumout. On the back of the bottle it says this:
Add entire bottle to nearly empty gasoline tank at time of oil change. Refill tank with 18 to 35 gallons of gasoline. Do not refill tank until near empty. Repeat every 3,000 miles at time of oil change.
So, this is what I did:
(1) CHANGE OIL
(2) SWAP IN NEW OIL FILTER
(3) POUR GUMOUT INTO GAS TANK
(4) DRIVE TO GAS STATION WITH NEARLY EMPTY TANK WITH GUMOUT IN TANK
(5) TOP OFF (20 GALLONS OF 87)
I'm just wondering if my drive to the gas station should have come before I added the fuel cleaner because if there was a gallon in the tank with the additive mixed in, then the concentration was very high compared to the lower limit of 18 gallons. Is a higher concentration of fuel additives bad?