Kawasaki recently released mpg information for their bikes on their website: http://kawasaki.com/mpg/mpgComparison.aspx

I am looking at their Vulcan line of bikes and it seems like the bikes with bigger engines give better gas mileage than the bikes w/smaller engines.

For example

Vulcan Classic 1500 = 33 mpg
Vulcan Classic 1600 = 36 mpg
Vulcan Mean Streak 1600 = 40mpg
Vulcan 2000 = 36 mpg

How do the 1600cc and 2000cc bikes have better gas mileage than the 1500cc bikes?

they are geared better, so they can sustain speed at lower revvs.because they have more power

My Northstar V8 has much better average mileage than most V6 cars

Quirks in match up of torque curve/ gearing?
l do not know how much to believe Kawi nos. - notice that a Vulcan 2000 Classic and the same LT get the same mph?
Did u look at other sources test nos.?

l can tell u that l get better then 36 mpg with my 1600 Classic based on the tire pressure l use & my riding style. These r not actual ratings & based on a formula. The 'mapping' systems for the F l system can be different & the gear ratios & tires sizes all contribute to these formulas used for figuring ''average all-around'' estimates.

On the link u provide there is a statement provided:

''Kawasaki is fuel economy estimates r based on EPA emission measurement TEST PROCEDURES. Your actual mileage may vary depending on how u ride & maintain ur vehicle, road & driving conditions, tire pressure, engine break-in, accessories, cargo, rider & passenger weight, & other factors''

Last year when the new formulas were applied everything, cars, trucks, & bikes all received much lower & more conservative estimates as a result