Originally Posted by lh4x4

I do a stage I breather and that increases back pressure some as I retain the stock exhaust which ups the torque a bit. Run 12.8 to 1 AFR which in the last hundred years of use in gasoline engines is the the fastest ratio to ignite and more complete burn.

Since all gas is about 115,000 btu's and the higher the octane and the leaner the afr the slower it burns and allows more unburned gas out the exhaust.

Now consider that one horse power is about 4,500 btu's. Then use a lower octane which burns more completely yielding more btu's in the power stroke.

The only problem is if there is pinging. The cooler 12.8 to 1 afr is less likely to ping. If it does just go to a little cooler plug. Don't do HD tune's as one of the few things it does is increase the spark advance which can make it more likely to ping.

The next step is if the bike did not come with an oil cooler add one. A cooler running motor runs stronger and lasts longer.

The final thing is use 87/89 octane. I put both because in my area one or the other is the cheapest at the pump.

Now more air in the same out with stock mufflers, 12.8 to afr with lower octane and cooler motor yields more power which requires LESS throttle to maintain speed. Therefore 50 mpg average is easy. Except for those who love to speed down the road. They will always suck up more gas but they don't care.

Initially with a new motor I do 12 heat cycles before it goes on the road. Then instead of 50 miles easy running as in the manual, I go 300 miles. Up the level to 1K then a little more over the next 2K. At that point my bike is ready to run.

That is the sum total of why my bikes yield 50+ mpg. Today on a 105 mile ride on my 13 TC96 Street Bob I got 60 mpg. It took 1.7 gallons to fill. Last week my 12 RGC CVO went 305 miles and took 5 gallons on the button for over 60 mpg. Now you see why I am serious when I challenge $10K that I can get 50 mpg. It is a sure win for me

Through the 2010 model HD gave the EPA highway rating of the bikes as 54 mpg and 42 average. From 11 on they only state 42 average. But it is reasonable to extrapolate that if the average is still 42 then the highway is still 54.

I confess that I can only get the 12 Vrod to 44 mpg once in a while but mostly 40 to 42.

I'm 73 and have been messing with high performance motors all my adult life. I'm the only Corvette/Viper owner that worked to get the highest mpg. Got the 09 436hp Vette to 34.6 mpg and the 06 510 hp Viper to 24 mpg. I had my Prius C to over 74mpg.

Right now I'm working on getting my 12 Ural 2WD to 40. It's only 27 now. I had it to 33 and made a wrong change.

Originally Posted by EricD10563

My high as been 47 mpg and my low is around 32 mpg. I've so far documented 67 fill ups and my average is 39.30. My gas mileage changes with speed more than anything, faster the sustained speed the lower it gets. If I'm running a steady 80+ the bike will never see 40mpg more likely around 36mpg or less. My bike as the 103 motor with a Stage 1 from Fuelmoto.

added: My 09 Road King with a 96 motor stage one easily averaged 42mpg and rarely dropped into the 30's mpg. I was so surprised by the difference I started to keep track and now consider it normal for this bike.