#2 and RUG

[probear]

My neighbor is a boat mechanic and ran into a slight problem with one of his clients.
Seems that his client topped off his boat with #2, while it was about 1/2 full of RUG.
We are presently draining off this mixture, but open to suggestions as to how to use approx 40 gals of fuel.

Also, assuming it is half and half, and he refills the 40 gal tank, what would the min amount to be left in the tank to dilute.

All suggestions appreciated.

Thanks,

dbw