Two things here, an engine will get better fuel economy under the same road and ride conditions after it has broken in. The engines are typically tight for the first 2,000 miles and it has been my experience they will generally cut loose after this. In my case this wasn't true as the FZ6 has been in the 45 to 55mpg range from after about 300 miles but I don't break mine in like the book says at all.
Now, as to this SV650 that gets 68mpg on a regular basis, I want to know who is pushing that bike or is it rolling down hill with the engine off? From anything I have read from their owners or even the Suzuki tests, the SV650 averages between 43 city and 54 hwy but this is corrected; meaning the odometer error has been eliminated. Somebody is pushing that bike or towing it with a strap....he he he he...
the SV confuses the hell out of me too, she can go about 200 miles and only need about 3 gallons on a typical commuting schedule. She babies the bike and does not weigh much at all. She also does not take it on short trips, she will only typically ride it if she is going over 20 miles away. There are many factors that we try to attribute it to but the bottom line is that when we pull over when riding together because i need gas (230ish miles on my old bike) and she only needs a little over 3 gallons.