I took a 5 and 2.5 gallon can to the local station and was surprised that I was able to put (if I remember correctly) 9 gallons in those two cans. I know that they leave some room for expansion but that seemed excessive. I contacted the state and they sent someone to check the pump accuracy. The reply was that the pump checked out OK so I guess there is a lot of extra room in those tanks.

I had another case which I have never checked on again but when we got our 2006 Grand Caravan last year the first time I filled it up I put in 20.2 gallons. As far as I know they come with a 20 gallon tank and in the last 20 years that I have been driving them I have never put in more than 18 gallons no matter how empty the tank was. I need to recheck this one and the tank may be bigger becasue it has the 3.8 liter engine not the 3.3 liter. It is funny that the owners manual does not tell you the size of the tank.