A long time ago I did some work for a company that operated fuel trucks for the railroad. The railroad owned the tank farm and the diesel, but they paid a vendor to fill up tanker trucks and drive them a 1/2 mi over to the tracks and fill up locomotives to the tune of something like 50,000 - 100,000 gal per day, and that was just at the one train yard, they serviced a lot of them all over the western US. They hired me to install an integrated GPS/POS computer with receipt printer, ID card reader, cellular connection to the server and fuel transfer metering system. Before, they had no idea how many gallons were pumped out of the tank farm or into any of the locomotives and they were fine with this for decades.
Then one day they noticed a large discrepancy between how many gallons were going into the tank farm and the expected fuel consumption of the locomotives. Somebody investigated and the story I was told was one of the fuel truck drivers was taking his rig out of the train yard every day with a partial load and driving to an empty lot right next to a freeway. He had made some sort of adapter that allowed him to transfer fuel into semi-truck tanks and he was selling diesel for $1/gal back when it was temporarily high - here in CA it was close to $5/gal for a short time. Th guy was selling 2,000 - 5,000 gal of diesel per day that he stole from the railroad and was pocketing $1/gal for it.
I don't know how long he did it before he got caught, but that's why they had me installing this system that tracked all of the diesel in and out of the trucks.
I wish we could find a guy selling diesel for $1/gal now!
