Denatured alcohol from the hardware store will work fine. It is very hydroscopic, so it will absorb moisture (which is also why you want to keep that stuff tightly capped). A gallon should cost you 7-9$, and will last quite a while. Good stuff to have around. In anything newer than a 617 you do NOT want any alcohol getting into the fuel, since the moisture will turn into steam inside the newer IPs (which are somehow different from the older ones, in a way I don't fully understand), and cause all sorts of havok.

But for flushing the tank on a 617, you should be just fine.

peace,
sam

__________________
"That f***in' biodiesel is makin' me hungry."

1982 300TD Astral Silver w/ 250k (BIO BNZ)
2001 Aprilia SR50 Corsa Red w/ 5.5k (>100 MPG)