I am looking at buying a Katana 600 and the guy I'm buying it from says he gets 30mpg.  All the research I've done says it should get 40-45mpg.  Is there something wrong?  Could it just be his driving style?  

I am pretty sure that ay research that you do will say that any vehicle is supposed to get better mileage than it really does. They want you to think it gets better mileage. And if you took it to the altitude they did with the right amount of humidity and temperature that they did the average mileage in. Well you would get the same amount if you drove your bike like a 99 year old that can not turn their wrist. So don't worry about the mileage and just enjoy riding becouse no matter how you look at it, it is still better mileage than your car or truck is getting. Plus it is a lot more fun to ride your bike than it is to drive your car. Be safe and ride smart.