68 MPG was with the stops, traffic lites and slow-go near and in between the 2 destinations. That city riding harms the average MPG's -but- the longer times at 50 MPH loafing in 6th gear on level roads to and from the congested area is where the phenomenal MPG realtime readings in the mid/upper 70's to low 80's raise the overall average. Even when I gas it up it usually takes ~3.4 gallons from a dozen miles on the low fuel lite. The great fuel economy is really unbelievable when you consider how fast the very same bike can accelerate to overnite-in-jail-speeds. Those 2 abilities do NOT go together. A bike that's fuel stingy always is among the slow. The fast bikes are gas hogs. The midsized F800ST has the designed in ability to grab the big performance numbers from both groups, but, of course, not at the same time!
To further answer your question, I do not know how bad it would be if I wailed on it for an entire tankfull, but crazy riding with a fast group at a recent Bash netted 62 MPG. Some riders at the other F800 site get low/mid 50's, but it's not stated how many cold engine starts, idling periods, sustained high speeds or frequent full throttle takeoffs they are doing.
To me that says the worst it will get coincides with the best an OilHead/HexHead Boxer will get. I have also proven it is on regular grade (Chevron/Texaco) gas too. The few times I put Plus/Mid grade fuel in it was at the Bashes, when I knew there might be sustained high speeds and sustained full throttle usage. Having the computer dial back the ignition timing or maybe boost the fuel injected in for regular gas usage would not generate the maximum performance that may be needed.
It's almost rare when I will spend a lot of $$ on a machine and later calmly be able to say it was worth it, but it is. Especially when I considered and rejected all the other bikes (R1200R) that fit my riding style.
