I have had this 05' Ultra for two years and over the last 47000 miles I've averaged 42 to 44 mpg (yea, I check it at each fill up). Until last week it was stock from the air cleaner to the pipes. But, because I felt the bike was losing a bit of grunt I added a Arleen Ness Big Sucker air cleaner and did a HD stage I download. I then took the bike on a bit of a ride from Yuma, AZ to Sioux Falls, SD and back. Over 3600 miles I averaged only 30 mpg! The lowest was 22 and the best was 36 mpg. What's going on???? I had a dealer in Abilene, TX check the codes and the right download was installed. He thought that my running the stock pipes was causing the poor fuel mileage, but I've read of people on this forum doing this same mod and their mileage was better than mine. Any thoughts?
Thanks,
Nomadic RAM

 

I had the same problem when I did the Stage 1 without changing pipes. I put a set of SE Touring slip ons on my bike (I wanted performance not sound). My mileage recovered to 38 - 40 Mpg

 

I went with the stage 1 air cleaner, v&h dresser duals with the ovals, and the fuel pak. My fuel economy pretty much stayed the same... around 46 mpg.

 

SE Slipons, K&N, PCIII....46 lowest, 49 highest running 75 on the interstate... 04 Road King... Sorry about your scooter...that is the pits....

Hogback

 

I have a carb 05 rk custom. I installed the se air kit and added drag fishtails (I wanted loud). I have always gotten 38-40 mpg, except on the highway...still not sure why. But now after sitting for a whileI am getting 32-35 mpg. I am on my second tank and hope it was just bad gas for sitting for two or so months. Will give my bike another tank or two before I freak. Still beats my truck at 20 mpg.-PapaTravis

 

I had the same problem with low gas milage at the beginning of the fall and the guys here on the forum said it was do to the change in the additives for winter fuel? I lost about 10 to 15%.

 

'05 Ultra also here.

I went from 44-46mpg stock to 32-36mpg with Stage 1, PCIII, Rush slipons.

MPG is the price you pay for more performance - that's what I've been told.

Even custom dyno wouldn't bring it back up.

 

After 47000 miles why would you do it half a$$, You added in more air and more gas, but you didnt give it a better way to get it out. I agree with the dealer, try better free flowing exhaust, or put it back stock.

 

I put it back to stock. I reinstalled the stock air cleaner and had the dealer reflash the bike back to stock (He only charged me $36 for the download). Prior to putting the bike back stock I did a 60 mile run at 80 mph and I got 26 mpg. After putting it back to stock I did the same 60 mile run at 80 mph and got 32 mpg. Normally I would have gotten at least 40 mpg doing that same run. I don't know what's going on but it's driving me crazy which will cause me to throw stupid amounts of money at the problem trying to fix it.

Going nuts in Arizona.

 

Could be you have other issues, efi injector problems or other things that effect the delivery and amount of fuel. After all things wear and you do have over 45k on the bike.