Anti-theft fuel caps

They can't steal what you don't have. Fuel at the start of your day, and park for the night with the tanks nearly empty. Provide easy access (no locking caps, no anti-siphon, just an easy to remove cap) for them to see there is no fuel in the tank (or at least not enough to waste their time taking) and they'll simply move on. After a few times they come up empty handed, they'll decide that it isn't worth the time/risk even bothering to check your trucks anymore, and they'll stop coming around. However, as long as the trucks are parked with full tanks, they'll remain targets. The harder you make it for them to get what they want, the more potential there is for them to retaliate by damaging your trucks as they take what they want.

The ONLY 100% surefire way to prevent fuel theft is to not leave fuel in the tanks. If you don't have it, they can't steal it from you.

 

Never underestimate a thief

 

So substitute diesel with sewage .. Check ..

 

I'd recommend a cordless drill and 1/2" drill bit. Less likely to draw attention than a punch and sledgehammer.......

 

Who is so enamoured with one product that you're flogging it in every fuel theft thread... riiiiiight.