I have gotten 49 on the highway with cruise set average about 45 usually I think the 54 number is at the bonneville salt flats with 70 psi in the tires ambient temp 72 runnig constant 55 stock trim

 

Stock 96 with cats. If I baby it, and stay between 55 to 60 mph, I can squeeze 52 mpg out of it. I average 48 mpg.

 

Stock 2011 Street Glide with 96" motor.
Get 43-46 MPG
That's riding in the mountains of WV.

 

09 96 with slipons got an average of 46 on a 3212 mile trip from Louisiana to PA. That was doing the dragon 129, and all the parkways and skyways etc.

 

I believe in controlled settings you could get the EPA est MPG.

On my bike I average 40mpg , 2011 with a Stage 1, SE A/C, V & H Power Duals and Black Out Rounds and a Power Vision Tuner . I get 40 as a daily average but I ride hard, almost every start is WOT shift at 5000 and above, a lot od canyon roads and freeway at 80 +.

I rode with some new riders last sunday and for one of the first times really just cruied, mostly 40 -70 mph canyons and a little freeway and I got 47 mpg, so i think it can be done

 

What the heck... V&H AC, V&H Duals, V&H 4" Rounds and SEPST + flat Florida = 42mpg. I adjusted the timing slightly and now get 45-46 mpg with the same set up.

Like someone said before, that advertised MPG is in such a controlled environment ans running gas w/out ethanol, you can get close, but hard to consistantly meet it.

 

I have a little over 15000 miles on my 2011 RGU and never have gotten under 40mpg usually mid to high 40's even running 75-80mph I am able to still get non ethanol gas and I think that helps. Also stage 1 vtuned tts. I think the roadglide fairing is more effecient too.

 

Did I mention I live on the Eastern Shore of MD not a hill for miles and miles and miles...

 

I've seen 51 mpg on my fuel moto stage 1 07 roadking. Cruising 2 lanes solo with @ ~ 55mph, with my 64 year old dad riding it i did see 54mpg once. For the most part if you are doing >55 your never going to see anything close to those numbers. I generally average about 38-40 and have dipped as far as 28. There are so many variables filling your tank also that hitting that magic number will be impossible. Though I have seen better MPG riding in colder weather about 55 *F just this weekend put up 50mpg running @ 65 mph with a slight tailwind.

 

Got the same set up as you on my 2010 Ultra. I checked it on a 125 mile trip. Keep it around 60 mph and got 48.6. Anything 55 and over I was in 6th gear.