I too trusted a gauge... ONCE... and ended up calling my bride for a gas can (on my Thunderbird). Since then I only go with the trip meter. Due to my tune and heavy hand, I get about 26 MPG mixed riding (city/highway). I think my V-Rod is getting about the same (1250cc's all stock); so I'm good with that. My last 'good gas mileage' bike was a Honda 750... I'm perfectly fine with trading a little gas for performance and enjoyment as it's my 'Road Therapy'...
-MIG