[Spyderman]

I'm thinking a big part of it is the nature of the engine, since its torque is at higher RPM's Can Am geared the Spyder so you are "in the torque" while cruising. Combine this with the extra weight and larger frontal area and the mileage takes the hit.

 

[Spyderman]

One thing the Spyder has to its advantage is its size, unfortunately that means more weight, and even worse, a larger frontal area. The resistance of moving an object through the air increase with the square of its velocity... so the faster you go on the Spyder, the bigger the impact of its frontal area. But I'd rather be seen on the Spyder, than not seen on a motor cycle!