Too easy to go downsteam from the tank if all they are after is the few gallons of diesel that a tractor holds. I would be concerned if I had thieves around how long it would before they figured out parts, or even the whole tractor are worth more than it's fuel. If your concerned that somebody is stealing diesel, you might want to secure it a little better, before diesel is just a side product of their efforts.
Diesel usually isn't the fuel of choice for thieves, and tractortrailers are usually better targets because they hold more (mine holds 300 gallons)
I know this doesn't answer your question, but trying to help.
David from jax
