Paul,
When I was a EC in town, the young after school shop boy with the company I worked for at the time proved why you should
always make sure that you know what the vehicle you are driving runs on.
The vehicle, a Mitsi L300 van was nearly empty, so as you do, he proceeded to fill it up.
I got a ring from my boss later on to tow the van back to the yard, because it was full of diesel.
I looked in the tank filler tube and yes it was.
My boss at the time even showed the young fella the label on the inside of the filler cap: 91 Unleaded Only.
At the PoCo, we have our own filling station and it only gives diesel.
Our whole fleet runs on it, so you could say it is idiot-proof.
However, to change the subject if I may, I like the idea of Bio-Diesel.