I don't think there is any reason to fear monger if it runs fine once drained... If you managed to get 4K out of the poor customer good for you, crappy for him, mistakes are made.
I ended up running mine on about a 50/50 mix from the top of the Hurley to Pemberton without any fatal damage and that was over 25000 kms ago already. I drained the tank and fuel filter, through in a few dollars of diesel and a couple cans of diesel conditioner and it fired right up with a little white smoke.
To be honest I got my best average fuel economy the following months and should probably get to changing that fuel filter.. Oh, and gas station that caused the hassle is now closed! booya karma's a bich.
So, moral of the story. Never let an attendant, or your wife, pump the diesel in your trucks!
