Extra fuel tank under dry van

That's a good idea; hadn't thought about that. I've seen reefer trailers with two fuel tanks; one on each side.

 

Someone correct me if i am wrong, but i think if the tank was just there for storage (as in not directly supplying the engine), then wouldn’t it be considered hazmat?

 

Once you figure out the fuel tax rates and wherever your discount locations are, most of it can be found for similar rates. It seems like it would be a lot of extra work for a savings of maybe a few hundred at the end of the year.

No room behind sleeper and across the cat walk?

 

If you put the tank behind the landing gear you will be looking at about a 3 pounds to trailer and 4 pounds to drive axles for every gallon added. I also have a heavy truck. I am always playing the fuel weight game.
Bobtail and full of fuel/def I am 21800 and trailer is 15200 when full.
Truck holds 225 and 20(?)def trailer 75

If weight is already an issue for you then why try to have even more fuel capacity?

 

Keep in mind that the difference in state prices is largely due to different tax rates. IFTA taxes ultimately are paid according to the miles driven in each state, not how much fuel is purchased. You will not be saving any money once IFTA is calculated and paid.
Your just going to be carrying around extra weight.

 

Learn how to leverage the fuel taxes to reduce the costs.

Also reduce the crap you have in the truck, I used 12 to 16 weeks out at a time and never had to carry much more than some food and clothing.