My missing gallon?

[Raprider]

I've been "religiously" tracking my fuel consumption on my ST-S using Fuelly.com since purchase, and in 18 months over 6100 miles, have an average of 29.8 mpg, pretty consistently in the 27-29 range. I'm also pretty consistent about how I fill up, always topping off past pump shutoff till I can see the gas, always 91 octane.

I ride mostly local stuff, think back roads at 35-65 mph range, lots of 3rd and 4th gear, and try to stay in the 5-6k rpm range on the V-twin. I'm not a burnout king, but I ryde it hard most of the time, about 50% of the time 2-up (130 lbs when solo, 250 when 2-up...plus my saddlebags and tail bag to add some wind resistance).

Today I decided to push my tank to the limit, with a known 3 days of back-to-back 50 mile round trips.
This morning as I arrived at my destination, my low fuel light came on at 125 miles on the Trip Odo, with 2 bars left on the gauge. I rode the 25 miles home, with ZERO bars on the gauge around 135-140 miles. At 150 miles on the trip odo, I filled up with 5.45 gallons.

Specifications state a 6.6 gallon capacity.
So...where's my missing gallon?
Or, did I have another 20-30 available till completely empty in spite of zero bars?
I know...YMMV...

[ARtraveler]

I rode my 10 RTS 184 miles and put in 5.8 gallons. I knew that was pushing it and have never repeated the process. The needle on the analog gauge was way below the empty indicator.

[Easy Rider]

Specifications state a 6.6 gallon capacity.
So...where's my missing gallon?
Or, did I have another 20-30 available till completely empty in spite of zero bars?
I know...YMMV...

It is still in the tank.
ALL gas gauges include a "hidden reserve" to try and make up for the "idiot factor".
Sometimes even that doesn't work.

Note: It is not good to run the tank completely DRY......and the absolute capacity of the tank may include some necessary air space.
There might not be 6.6 gallons of USABLE space.

[Peter Aawen]

You REALLY don't want to run your tank dry! Your injector system & fuel pump rely on the fuel remaining in the tank as both coolant & lubricant, so running it down too low means those components start overheating & excessive wear! You might get away with running it til it stops once, maybe even a few times, but the risks are great & the wear is usually the sort of stuff that means your engine might continue to run ok, but at a lesser efficiency & worse fuel economy, and the only way to fix that will be to replace the components that've worn, ie, fuel pump, injectors, etc.... the difficult to get at expensive stuff!

So maybe you should just work on that 150 miles being your 'usual max range' & if the low fuel warning light comes on before you expect it to, seek fuel sooner!

[Raprider]

I agree, Peter! I had been working on 120 miles being my 'max range', and wanted to see how much further I could go.
I admit the "clench" factor was in play

It was 90 or so today, and the temp gauge stayed at its usual 4 bars.

[Bfromla]

If gas was from same station every time you filled up then the estimate could be more accurate, with all ethanol mixing &
Summer blends there’s really no telling.

[Motorcycledave]

I've been "religiously" tracking my fuel consumption on my ST-S using Fuelly.com since purchase, and in 18 months over 6100 miles, have an average of 29.8 mpg, pretty consistently in the 27-29 range. I'm also pretty consistent about how I fill up, always topping off past pump shutoff till I can see the gas, always 91 octane.

I ride mostly local stuff, think back roads at 35-65 mph range, lots of 3rd and 4th gear, and try to stay in the 5-6k rpm range on the V-twin. I'm not a burnout king, but I ryde it hard most of the time, about 50% of the time 2-up (130 lbs when solo, 250 when 2-up...plus my saddlebags and tail bag to add some wind resistance).

Today I decided to push my tank to the limit, with a known 3 days of back-to-back 50 mile round trips.
This morning as I arrived at my destination, my low fuel light came on at 125 miles on the Trip Odo, with 2 bars left on the gauge. I rode the 25 miles home, with ZERO bars on the gauge around 135-140 miles. At 150 miles on the trip odo, I filled up with 5.45 gallons.

Specifications state a 6.6 gallon capacity.
So...where's my missing gallon?
Or, did I have another 20-30 available till completely empty in spite of zero bars?
I know...YMMV...

I don't trust mine on my 2008 GS as far as I can through it... I have learned the hard way
to always carry a 1 gal. sealed gas container when I go on a ride longer than 110 miles unless
I want to push it. I have never got better than 25.2 mph... my Buick gets 30.3 always and
carries 5 people and luggage. ???????
On the up side I did not buy the Spyder for gas milage, only for fun and safety

[ARtraveler]

An additional point...Linda and I are not "iron butt" types of riders. We like to go and enjoy wherever we ride. Many times, we stop just over 100 miles to get off and stretch. It feels good to get off the bikes and just relax. Many times, we make it a gas and a pit stop as well.

Since she still has a 998, we mostly get our gas no later than 150 miles...when her fuel light goes on. So....the bottom line is, most of the time we refill the tanks between 100 and 150.

[Raprider]

Agree with you there, AR...these bones definitely need a break, usually sooner than 120-150...

[AeroPilot]

All liquid storage tanks including gas tanks allow for "head space" for expansion with changes in temperature. Don't count on the last gallon of capacity especially on the RTs since their fill spout is on the side of the tank. Even with the F3s larger tank capacity the actual usable volume will be between 5 and 6 gals... Like page 7 in the manual advises never top off.

Fueling the same way and averaging results over several tanks will give your best number for how and what you ride. For us on the 1330 platform that means fueling around 180-200 miles usually with around 5 gals required.