Like all the others have been saying...no change in fuel economy, but big change in riding pleasure. I run 87 octane fuel and average 32-34 MPG on the highway traveling 60-70 MPH. There is significant popping, however, with the pipes and factory tune. Upgrading to Tuneboy tune or PCIII will decrease or eliminate the popping, but the down side is slightly lower fuel economy as the tunes add fuel to the system at zero throttle position, or so I'm told. The extra power boost and attention getting sound is worth the lower economy. Besides, a 6 MPG reduction in fuel economy only costs you an additional $2.50 at fillup time, to go the same distance...worth the cost to me. 8)