Maybe we should average everyone's reported mpg to get the definitive, final, one-and-only-answer to the original question? How many mpg does an ST1300 get?
snip ........
Both bikes showed 5-10 mpg lower at lower elevations, and 2-5 mpg higher at high elevations.
My 98 st11 averaged 50.3 mpg over 85 tanks, 40.4 low, 56.6 high. It had a +2" windshield, k&n air filter, otherwise stock.
My 04 st13 averages 50.3 mpg over 249 tanks, 38.2 low, 61.3 high. It is totally stock other than added fairing and mirror air deflectors.
Both bikes showed 5-10 mpg lower at lower elevations, and 2-5 mpg higher at high elevations.
That is interesting !! How do you define lower & higher elevations ??
Someone needs to put a turbocharger on their bike. That would be interesting to see how that would work in higher elevations.
If you ride at the elevations here in Colorado most of the time and them go to 1000 feet or less it is like having a turbo on the bike. Like John mentions more mpg for less HP. Somewhere in the neighborhood of 5% loss of HP per each 1000 foot rise in elevation.
An interesting manifestation of this altitude phenomenon is that small planes (normally aspirated) are more efficient the higher they fly but their engines also may put out only 50% of their sea level power at altitude. Eventually, they hit their 'ceiling' and can fly no higher. Same exact behavior as what we are talking about but presumably, planes routinely fly higher than most of us ride.
This is related to what I said earlier. Change one of the design parameters and others are affected. Here we are increaseing oxygen in the air per unit volume as we go to lower elevations, increasing the power output, and decreasing the fuel economy. Adding the supercharger (or turbocharger - both do the same but get the power for the compressor differently) simply crams more air/fuel into the cylinder and ups the power. Burn more fuel, get more power, you will lose a few mpg.
I read that a turbocharger is ideal for an airplane engine. It is desirable because it "maintains" power at higher elevations ( compared to at ground level ) , rather than increasing power at higher elevations.