We've got all the car numbers that we are fueling along with the quantity and flavor of fuel that they need posted in the pit. In the six years I've been doing itg we have NEVER dumped the wrong flavor in a car at our pit. Trust me, we know EXACTLY which trucks are taking diesel. None of us like dumping diesel, it's heavier than gasoline, and it doesn't evaporate out of your fire suit if any gets spilled. That and for what ever reason the Hummers (H1 or H2) fuel filler locations generally suck, they are too high off the ground for an easy stick with the fuel cans.