I think you'll find that in whatever situation you find yourself, the gear that will require the least amount of throttle will be the highest-mileage gear.

If it takes 8% throttle in 5th @ 55 or 9% throttle in 6th, obviously there won't be a great difference, but you'll achieve the greater mpg in 5th, even at the higher rpm. The motor will be working more efficiently / easier at the lower throttle pressure, and that's the difference.

If the initial question could have been more along the lines of "will the IDS reduce mileage at all?" it probably does; negligibly. If the rubber bushings and the extra bearing heat up as a result of being in service it's an indication of energy being lost in the system. I'm sure they do and there is. Even if it's only on a "microscopic" level.

 

I seem to be getting a little better milage after the instal also. I still find myself in the higher RPMs sometimes. When I finally break 11,000 miles of habit it will most likely get even better.

 

I've had my IDS on my 07 Ultra for about 2,000 miles, I check
my gasmileage at every fill up on all my bikes and my mileage
is still between a low of 44MPG to a high of 52MPG..

I don't see any change at all on my gas mileage with the IDS..