Hey guys, so, my gas gauge is behaving peculiarly and I wanted to see if you folks were experiencing similar.

When I gas up my '18 Fat Bob, the gas gauge shows full bars, and the remaining miles indicator says usually around 185 or 187. I zero out the trip odometer at this point.

Over the course of the next 100+ miles, these two will stay usually in sync; the remaining gas gauge plus the trip odometer will usually add to 187. So after I've driven 87 miles, the remaining gas gauge says "100". After I've driven 100 miles, the remaining gas gauge says "87".

This continues until the red light comes on, usually at about 47 miles. At that point, I will have driven about 140 miles. Now here's where things go wacky -- the remaining miles gauge will run out RAPIDLY. It behaves 'til about 40 miles left, then it plummets like a stone, dropping down to 5 miles left over the course of driving 17 miles. I did that drive today -- it hit 47 miles, the light came on. I drove 17.5 miles to the gas station, and it was showing "LOW" for the last five miles and sucking fumes. I filled it up with 3.35 gallons, which means there was only about .15 gallons left in the tank.

So, in essence, the gauge is lying. I was never going to get 187 miles out of a tank in the first place; I got an actual 155 miles out of the tank, and when I refilled the tank took 3.35 gallons, for an actual observed 46.3 miles per gallon, right in line with Harley's claim of 47mpg. But that last 17 miles is a nailbiter; you think you've got 40 miles left in the tank but in reality it's more like 22 at most. I had maybe 5 miles worth of gas left in the tank, so the actual maximum range is 160 miles; when it starts out saying "187" it's clearly overstating the claim by a good 27 miles, and then seems to take 'em all back over the course of that last 2/3 of a gallon.

It's not just once, I've run into this three times. It's consistent behavior.

Is this typical behavior? Are you guys running into similar behavior? Or do I need to take this in to the service?
Thanks!

 

Electrical gremlin in the gauge I'd say.

 

Doesn’t the mileage on the gauge adjust with how much you twist the throttle open?

 

It seems to me that it's a running tally of how many MPG you've been using for a while. It doesn't immediately respond to changes, but if you get up to 75mph and keep it there for a while, then the gauge will adapt and project the remaining range at the current rate of fuel use.

What I'm encountering is that it's quite consistent down to about 40 miles remaining in the tank, then it drains down incredibly quickly, at 2x to 3x the normal rate, until it hits LOW. It's that part that seems abnormal. I get that it was never going to get 187 miles out of a tank anyway, but if it's gonna lie I'd really rather it lie to me about how far the full tank will go, than how far the empty tank will go.

So I suspect that either my low-fuel light is coming on too late maybe? Or there's a sensor that's not properly sensing how much gas is in the tank? Or, maybe it's operating normally and they all do this (hence asking for confirmation)? Thanks for any feedback!

 

Might be the shape of the tank too ,there's less volume near the bottom than say half a tank .

 

All Harley fuel gauges are never accurate. I always go by miles ridden to fill up the tank

 

It has a 5 gallon tank, not 3.5. Mine did the same thing at first. It will settle in after a while. The more you work out that right wrist, the less you gonna get. I've gone as much as 207 miles before the gauge says LOW. That was steady riding at 60 mph or under.

 

+1 NEVER rely on the MTE (miles to empty). Its calculated by your riding habits (i.e. twisting the throttle). As Pothole has stated, try riding at a steady speed/rpm for a long distance and you may see the value increase.

 

Negative. A 2018 Fat Bob has a 3.5 US gallon tank.

I think the bike's ECM probably calculates remaining range based on the last 30 miles or so average of fuel used.

OP - I haven't noticed that behaviour on mine. It's been pretty accurate so far. It does annoy me that the LO indicator comes on at 1/4 tank though, but I haven't noticed the gauge or the range indicator decrease any quicker at that point.

 

Never trust electronic fuel gauges. On any new bike I buy, I will fill the tank, reset the trip meter and ride until the low fuel light comes on, then note the mileage, fill it up again, note how much gas it took and calculate range based on mileage and tank capacity. I calculate my mileage on every tank of gas to note any changes. I do the same when I fly.....note how many pounds on board and calculate flight time based on fuel burn. I then reset the clock to 12:00, so if the fuel gauge takes a crap, I know how long I've been airborne and how much time remaining in the tank. On the new Fat Boy the low fuel light comes on at 150 miles.....but I still have enough gas to go about 190 miles.