Hey guys. I believe to have a problem with gas mileage on my f4i. I've measured the mileage from 0 at a fill up and got 106 miles when the fuel reserve indicator has turned on. Isnt that weird? I've done some research and read up posts in which guys are talking about easily getting 180 miles on a full tank. Should I be worried?

 

Well there's only 2 reasons for that low miles per tank: she's really drinking that much or she's only "reporting" it.

There's actually a lot of guys that had problems with the fuel pressure regulator going bad ( do a quick search for FPR ) and a few others with the fuel reserve sensor in the tank.

Next time that you fill her up take notice of the amount of fuel that you actually put in. If you put around 14.5 liters she's reporting ok and it probably is the FPR.
If it shows the reserve bars and you put let's say 10 liters, then it's the fuel reserve sensor.

 

That seems to me like it's a bit of variation in riding. So you got 70 miles less than the guys that SQUEEZE 180 out of their F4i. If you ride politely all the time, and don't exceed 5,000 rpm, you'll also get 150 miles out of your tank. Try to ride at your easiest, and see if you still get 108 miles out of your tank. If you consistently get 108 or 110 out of your tank, and you're being very gentle with it, then I would look into the FPR. My F4i got about 140 to the tank with some spirited riding, but not out of control. I would take an average first, not just go off of one tank of fuel.

Another thing to think about is your mods. If you are geared, or have a slip on, stacks. etc. Some exhausts require a tune so the bike doesn't run rich as a pig, which I'm sure you know seeing as you've been on here for a while. So make sure it's not just an easy maintenance thing before you go replacing FPR's and various sensors.

To answer your question: No, you should not be worried. You're not throwing any CEL's (that you mentioned) and 108 isn't THAT bad. Could be something easy, could be something deep. But at 108 to the tank, you're getting ~22 miles to the gallon. Try a different fuel (premium if you don't use it..), and ride like your 76 year old neighbor on their Vespa, and see what happens with MPG's then.

 

+1 what Junior said. Right now I would say you don't have a MPG issue. Some will claim they get 180-200 miles before fill up and others only get 100. You're not too far from me and I never thought I had a MPG issue. I would say if your getting 80 miles then you have a MPG issue.

 

Thank you for your input guys. Every time I get about 110 miles BEFORE the reserve indicator kicks in. And yes, I've been using nothing but the premium fuel. As far as riding goes, I tend to do 6-7k of rpms on the freeways. I was also wondering about how to keep the rpms and whether it's better to keep them high with a lower gear, or low with a higher gear.

 

As a side note my bike runs better on 87 octane than 91.

 

what do you mean by 'better'? 87 is a dirty fuel i would say, since it does not burn as well as 91 and leaves more residue in your engine. am i wrong?

 

Yes, you are wrong. 87 actually burns more easily than 91.

 

The difference between 87 and 91 is not the quality of the gas but their ability to ignite. So 91 is harder to ignite that 87. Motors with high compression motors use 91 or higher because the high compression has a tendency to prematurely ignite lower octanes. Try to put 87 back in and see if you notice a difference.

As far as RPM's go I will always choose a lower RPM in a higher gear while cruising. The lower RPM will give you better fuel economy and it is not harmful to your motor as some think. The only downfall is your not in the real high RPM where all the power is in these 600 so when you punch that gas it might not take off like a raped ape but it should still be plenty enough especially to pass a car as long as its not a Z06 Corvette or Viper.

 

I used "better" for a reason. It is very generic and based strictly on my opinion. As they say "we all have one and it dont stink" Their are so many variable involved in my "better" feeling that I couldnt possibly cover enough of them to convey my feelings into facts, I leave that to the liberals Lets just say that during the summer when I first got this bike I used 91 exclusively. As I gathered more info here and the manual I realized this bike was built to run 87 so I tried it and the bike just "felt better" and was to spec and is cheaper. Whats not to like