2016 RT greatly reduced mileage in cold weather

[BMW RT Pilot]

And I always thought cooler, denser air was good for power production.

 

[JAVGuzzi]

It is, but not for drag. And several Riders have claimed they get better mileage at higher altitudes than at lower altitudes, and I believe that, even tho at a higher altitude, less power can be produced. I don't understand why a higher altitude should give better gas mileage, except for the thinner air and less drag.

 

[BMW RT Pilot]

I need a drink. Lots of drinks.

 

[Stephen!]

Rolling resistance of the different kinds of pavement could make a difference as well. On Guam, where they used coral as a substrate and the travel paths are polished glass smooth, the roads have little resistance to anything. Whereas the highways in southern Nevada seem to be extremely rough beause they chew up a set of tires in no time and a tank of fuel doesn't seem to last nearly as long. (Yah, that's my story and I am sticking to it...)

 

[Stephen!]

It is, but not for drag. And several Riders have claimed they get better mileage at higher altitudes than at lower altitudes, and I believe that, even tho at a higher altitude, less power can be produced. I don't understand why a higher altitude should give better gas mileage, except for the thinner air and less drag.

Because of the reduced O2 density the O2 sensor tells the computer "there is less air, use less fuel to maintain the correct Air/Fuel mixture".

 

[Stephen!]

And I always thought cooler, denser air was good for power production.

Mostly it's about drag. Keep in mind as speed doubles, drag quadruples. The drag at 50mph is four times the drag at 25mph and the drag at 100mph is four times the drag of 50mph. This is why "dyno" speeds are not reflective of what you can expect on the track.

 

[JAVGuzzi]

Yup to the above, and rolling resistance is much smaller than aerodynamic drag. I don't think a difference in rolling resistance due to a change in road surface can make 10% difference in gas mileage.

 

[JAVGuzzi]

Because of the reduced O2 density the O2 sensor tells the computer "there is less air, use less fuel to maintain the correct Air/Fuel mixture".

Ya, but I have read that bikes with carbs also get better mileage at higher altitudes.

 

[DrNeo]

Because of the reduced O2 density the O2 sensor tells the computer "there is less air, use less fuel to maintain the correct Air/Fuel mixture".

Technically at the altitudes that we ride, it's the pressure that isn't as high - O2 concentrations are the same, but as you said, the density has changed. Big pet peeve of one of my undergrad professors

 

[Stephen!]

Technically at the altitudes that we ride, it's the pressure that isn't as high - O2 concentrations are the same, but as you said, the density has changed. Big pet peeve of one of my undergrad professors

True, the ratio doesn't change, but for a given volume of air there will be fewer molecules of every gas. Including O2. As for altitudes, I've been at altitudes on the bike where the FAA requires me to be on supplemental oxygen while flying....