Reserve Miles for Motorcycles - Fuelly Forums

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Old 09-04-2008, 02:43 PM   #1
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Reserve Miles for Motorcycles

It would be nice if Fuelly calculated the number of miles a motorcycle can go on its reserve tank at the MPG it gets. Knowing this is one of the reasons I track my mileage, so having it available in Fuelly would mean I could abandon the spreadsheet I keep. This would require an input for the size of the reserve tank, and a simple calculation.

Many (perhaps most) motorcycles have no fuel gauge. What we have instead is a trip odometer and a "reserve tank" (really just the last half gallon or so in the tank, not a separate tank). The effect is that until you flip that switch, if the bike still runs, you still know you have half a gallon of gas. When your trip odometer gets close to the number of miles you can normally go on a tank, you know to be careful not to get too far from a gas station, but how far is too far? Since MPG varies so much, we really rely on knowing that last half gallon is there. Otherwise we'd be stopping to fill up just on a hunch, only to find out we've gotten superb MPG and didn't need to waste time (and miles) finding a gas station--or worse, running out of gas.

So far Fuelly does tell us when to start being worried, but doesn't tell us how worried to be. When I hit reserve, should I pull over at the next exit and beg, borrow or steal a gallon of gas? Or can I make it to a station with favorable prices?

Naturally, this would need to be a per-fuel-up calculation so we'd know what kind of riding gives us how many miles, but an average is always nice too.
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Old 09-04-2008, 04:25 PM   #2
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We do currently show a stat of your average distance driven between fuel-ups, is that good enough?

Can you share the calculations you do in your spreadsheets? I have no idea how to calculate what you are asking for, and I don't own a motorcycle. I would just think when you hit a reserve you just look for a station, but your reserve is highly variable?
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Old 09-05-2008, 01:18 AM   #3
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don't reserves vary from model to model?? besides, if your reserve is half a gallon and you know the mpg of your bike, it wouldn't be hard to figure out - half your mpg...

i have a gas gauge but i don't rely on it. i use the trip odometer. i have a determined number of miles i'll go on a tank. i don't know how many miles i can actually go because i don't want to run the tank out just to find out (and i don't have a reserve).

depending on where i am, i'll determine how soon to start looking for a station... in the city, i'll go closer to my predetermined number of miles. when i'm in the country and in unknown territory, i'll obviously be a bit more prudent and fill up earlier... pretty much just using common sense...

am i missing something?? is there an advantage to squeezing every last mile out of a tank??
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Old 09-05-2008, 01:46 AM   #4
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Yeah, I think the calculation would just be trip fuel economy divided by reserve tank size, which would have to be input by the user. As a motorcyclist in a well populated area, I would have to say just tracking average distance between fuel ups is ultimately more useful. My mileage doesn't vary that much, and I hate to get to the reserve anyway. I've had the fuel tank apart, and on my bike there's an in-tank filter that gas goes through when the petcock is in the "On" position, but is bypassed when it's in the "Reserve" position. I use an aftermarket in-line fuel filter anyway, but if you haven't put one on your bike, I wouldn't recommend relying on the reserve too often.
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Old 09-05-2008, 05:45 AM   #5
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If reserve is the bottom part of the tank, then wouldn't the fuel mileage be the same as for the top part?

I ask, because, I am happy with the calculations.
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Old 09-07-2008, 11:05 AM   #6
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Just a note of caution about reserves - had a guy I used to ride with years ago that always liked to ride until the engine sputtered - meaning he had run out of fuel. He'd then switch over to reserve and start looking for a gas station. One day he did this, and the engine continued to die. He had no reserve and was out of gas. Turns out that on his old BMW, the "normal" position of the switch caused the gas to be pulled from a small pipe that stuck up about a half inch above the bottom of the tank, and when you switched to reserve, you drew that last half inch or so of fuel. His was an older bike, and the little pipe had fatigued and broken off, so he was drawing from the bottom of the tank all the time. Now, I think that most modern bikes use some sort of electronic sensor these days, but I always wonder if that system might fail, so I keep an eye on my miles since last fillup. The few times I have run all the way down to the point where my reserve light comes on, I've found it to be completely accurate (1.1 gallons remaining - I once had it turn on about 500 feet from the gas station)
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Old 09-07-2008, 12:27 PM   #7
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I prefer to run my gas down to reserve, and to push past reserve a bit when I feel I can safely. For example, if I hit reserve on the way to work, I usually fuel up at the station near my house when I get home in the evening.

The reason I like to run it as close to dry as I safely can is that sediment collects in the bottom of the gas tank over time. When you switch to reserve, you get that sediment in the gas that goes to your engine. If you hit reserve frequently, there's just a little bit of sediment each time, and it doesn't cause any problems. But if you always fill up before you hit reserve, you just keep collecting sediment. Then one day you're really in a bind and you have to use reserve, only it's now all full of gunk that clogs up your carbs. (Not sure of effect with fuel injection.)

The calculation is just the reserve tank size times the MPG. If the reserve tank is a half gallon it's pretty simple, but the size varies. This really is not a high priority issue, but for me it would be a definite "nice to have."
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