2017 R1200RT reduced fuel economy

I track fuel economy on every tank of fuel that goes through my 2017 R1200RT. While it's never met the standards that BMW claims, I usually average between 42 - 45 mpg riding long interstate distances here in the great plains. Just last week my average fell to 35 - 38 mpg. I know this isn't a closed course test. But the loading of the cycle with a solo rider is the same. Also scheduled maintenance is up to date. When I returned home I scanned for error codes using my GS911. Only one was present, Tank Switch Error. Can someone explain what this code means? I have attached a screen shot of the results.

What riding mode are you riding in? DYNA will use more fuel.

The only "tank switch" I can think of would be an interlock or sensor on the tank's gas cap - is that closing properly and securely? If it isn't, maybe ordinary evaporation and/or airflow is wasting your gas, or a faulty switch?

That "Tank Switch Error" along with Sirius XM Antenna Open and a couple of transitory nuisance codes are just that...clear them unless you really are not getting the radio to work or you think there is a significant problem with your gas tank latching mechanism.

One off's are not something to get concerned about and can be the result of many, many different factors...none of which can be diagnosed or troubleshot thru any forum or board.

This is very similar to any effort you have to go on a diet and loose weight....don't get on the scales every day to see how you are doing.

Sorry, this is not a solution, but the philosophy of ownership is up to every individual and trying to solicit advice on a forum is too much like getting on social media to post your daily coffee selection.

During the accumulation of mileage getting close to scheduled maintenance is always a time to access whether you could enjoy some better performance/ride satisfaction by doing the service early.

Replacing the plugs alone could be the solution to this issue, but like they say, everyone has an opinion.

Gas stations are switching to winter blend gas, but that alone would usually only account for about a 1.5-2.0% drop in mileage.

nyfty said:

. Just last week my average fell to 35 - 38 mpg. ]

Click to expand...

Was this one tank or several tanks?

Lee said:

Was this one tank or several tanks?

Click to expand...

Good question as I suspect too much ethanol in the gas.....
I'd try a tank or two non-ethanol and go from there. I have similar milage issues with ethanol in my 2018 GSA...YMMV

zenwhipper said:

What riding mode are you riding in? DYNA will use more fuel.

Click to expand...

Riding in NORM mode

Lee said:

Was this one tank or several tanks?

Click to expand...

Five fill ups over two days. Traveling in Iowa mostly at Iowa’s interstate speed limit. With about 60 miles of Iowa two lane at 55 mph.

nyfty said:

Five fill ups over two days. Traveling in Iowa mostly at Iowa’s interstate speed limit. With about 60 miles of Iowa two lane at 55 mph.

Click to expand...

That rules out a bad batch of gas or accidentally getting E85.
Three different times we got some weird gas and both bikes dropped their gas mileage by 8 to 10 mpg.
No change in our speed, the wind speed or wind direction. Next tank-full our mileage went back up.

With five fill ups over two days something is up.

Did you recently disconnect the battery or have it go dead?

That leaves valve settings, air filter and spark plugs.... My 0.02 Cts.