I have a 2006 SV650n ("2nd gen", "naked" F.I.).
Best I've done is 58 mpg during moderate backroad riding on Ethanol-free Premium. Straight hwy I run about 55MPG at 72-74MPH. I found Ethanol-free 87 at the end of last season, and may try to see if I can get some better numbers.
I geared it up 1 Tooth on the countershaft to drop revs about 500 at cruise and have a slip-on muffler.
It will do low 50MPG in-town as well.
Check out
www.svrider.com for everything SV.
Jay