well, i put the additive in with my gas, and im getting the correct gallons used, but my gas meter is moving up and down all the time. so far i have used 12.2 gallons. i thought it had an 18 gallon tank, but i would like to be sure, and im not sure that the low fuel light will come on when i get low. thanks.

18.
All vehicle fluid quantities can be found in the Owner's Manual.

man, i have looked. what page?? not that i dont trust you, i just wanna see it.