Still getting crazy gas mileage!

pugbuddy · Post by **pugbuddy** » Fri Dec 30, 2011 4:26 am

I still seem to be in a pattern of 66-ish mpg, 76-ish mpg, followed by 90-ish mpg! For the life of me, I cannot figure out why my mileage is all over the place. I use Fuelly to track it.

Given that it's just a matter of dividing the miles by the amount of gas entered in the tank, I would expect some consistency but it is just not there. My riding patterns are pretty much the same every week (up SH 75 to work and back; occassional side trips for lunch or groceries. Church on the weekends along with more side trips for various stuff.).

The only thing I can think is that the first mpg is mainly the highway (high speeds = lower mileage?) and the second is split between the week and the weekend. But I only fill up twice a week so why it would be split into three regular mpg ranges? I'm at a loss on this one.... Any thoughts?

2wheelNsanity · Post by **2wheelNsanity** » Fri Dec 30, 2011 7:59 pm

You to. I thought it was just my 170i and the winter fuel. I go from 75 to 85 all the time and I try to keep the speed at or under 55mph. Of course like you most of my miles are highway (90%). I would like to know what the 170i gets if riden only intown under 50mph.

Skootz Kabootz · Post by **Skootz Kabootz** » Fri Dec 30, 2011 9:00 pm

Lots of things can make milage vary - uphill, downhill, prevailing wind direction, temperature, correct tire inflation... mine varies constantly. It is your average mpg that is telling of fuel performance.

Silver Streak · Post by **Silver Streak** » Sat Dec 31, 2011 4:23 pm

It never ceases to amaze me that some folks don't understand normal variability in calculated fuel economy from tankful to tankful, and then think that using some totally unnecessary widget like Fuelly should somehow solve the "problem."

First, fuel economy calculations for a scooter with a small gas tank are -- by their very nature -- going to vary all over the map when you look at a single tankful at a time. Even if your riding habits and the scooter's performance were perfectly consistent (which they aren't, of course), getting consistent results from tankful to tankful requires that you fill the tank to exactly the same level every time. Given that the tank on a Buddy is so small, and that the only point for reference in filling is the hole in the plate welded inside the tank, refilling to the exact same level is essentially impossible. The plate in the tank is welded in at a fairly wide point in the tank where even a 1/4" difference in fill level will correspond to a significant difference in volume.

Second, fuel economy tracking software like Fuelly doesn't do a damn thing to ensure the accuracy of the fuel economy calculation. It simply provides a place to log and access your pump and odometer readings, and does the long division for you. A pad and pencil does this just as well (presuming you learned to do simple division in arithmetic class) and is just as convenient. Fuelly is just a pseudo-high-tech crutch.

hal888 · Post by **hal888** » Sat Dec 31, 2011 9:05 pm

2wheelNsanity wrote:You to. I thought it was just my 170i and the winter fuel. I go from 75 to 85 all the time and I try to keep the speed at or under 55mph. Of course like you most of my miles are highway (90%). I would like to know what the 170i gets if riden only intown under 50mph.

rkcoker · Post by **rkcoker** » Sun Jan 01, 2012 12:07 am

Another variable in this is where and how you cut off the gas fillup. I try to fill it back to the same same spot visually in the filler neck. It's the only way I can think to cut down the variables in this.

hal888 · Post by **hal888** » Sun Jan 01, 2012 1:37 am

Obviously haven't yet mastered the 'reply ' button (':oops:')

Just mentioning I'm averaging about 96 mpg with a 170i. I'm primarily riding on rural roads, almost always at 50 mph or less.

jrsjr · Post by **jrsjr** » Sun Jan 01, 2012 1:56 am

Silver Streak wrote:...Fuel economy calculations for a scooter with a small gas tank are -- by their very nature -- going to vary all over the map when you look at a single tankful at a time.

Yep, especially with such a small tank, I'd say add up the mileage for 10 tanks and divide by the total gas filled and you'll have a pretty good average number. WIll Fuelly do something like that for you retrospectively?

TVB · Post by **TVB** » Sun Jan 01, 2012 2:44 am

jrsjr wrote:
Silver Streak wrote:...Fuel economy calculations for a scooter with a small gas tank are -- by their very nature -- going to vary all over the map when you look at a single tankful at a time.
Yep, especially with such a small tank, I'd say add up the mileage for 10 tanks and divide by the total gas filled and you'll have a pretty good average number. WIll Fuelly do something like that for you retrospectively?

Fuelly gives you an overall average (the figure that shows up in my sig), and can also give you any of a bunch of other figures, on whatever time frame you want (e.g. best miles/fill-up in the last 3 months, total gallons used in the past year). It also generates graphs showing (for example) your monthly average for the past year. One of their standard calculations that shows up on your accounts "dashboard" happens to be the average of your last 10 fill-ups. Nothing you couldn't do with pen and notepad and a calculator with graph paper, or with a spreadsheet program, but they've done all the work for you, so I find it convenient.

pugbuddy · Post by **pugbuddy** » Sun Jan 01, 2012 5:35 am

getting consistent results from tankful to tankful requires that you fill the tank to exactly the same level every time

No, it doesn't. It only requires that you know how much gas you put into the tank every time, which is measured for you at the pump. When you divide by the mileage ridden, that gives you the mpg for that tank. It's not rocket science, I agree. But there is no requirement to put the same amount of gas in the tank every time.

The other part is that this is a recent phenomenon. As recently as early 2011 my gas mileage was consistently in the 90 mpg+ range. There were no "dips" (over 3-5 mpg) in the mileage at all. Now I'm seeing variances of 20-30 mpg on a regular basis. That change doesn't make much sense to me.

Lots of things can make milage vary - uphill, downhill, prevailing wind direction, temperature, correct tire inflation... mine varies constantly. It is your average mpg that is telling of fuel performance.

Mine is varying--quite consistently--up to 20+ mpg. Since my riding habits are consistent (not perfectly so, of course, but they don't vary that much), I'm not certain why there is such a huge variance in mpg. And it's like clockwork--the first fillup of the week is in the mid-to-high 60s; the second in the mid-to-high 70s; the third in the 90s. I'll probably never know for sure but it's one of those things that suddenly turns up and makes me go "What the heck?".

Southerner · Post by **Southerner** » Sun Jan 01, 2012 2:14 pm

Motorcycles (and scooters, I would assume) do vary a lot more than cars. Still, SOMETHING different happened between the time it was getting consistent mileage and what it's doing now.

If you really want to track it down, you will have to take into account all the variables and try to eliminate them. Same type of gas every time, same driving route in the same conditions (like stuck in rush hour as opposed to better traffic conditions), etc. It could get pretty tedious.

I guess it must be the fuel injection, but if you 170 is getting mileage THAT good, even the lowest figure, it rocks in my book.

PeteH · Post by **PeteH** » Sun Jan 01, 2012 2:26 pm

pugbuddy wrote:
getting consistent results from tankful to tankful requires that you fill the tank to exactly the same level every time
No, it doesn't. It only requires that you know how much gas you put into the tank every time, which is measured for you at the pump. When you divide by the mileage ridden, that gives you the mpg for that tank. It's not rocket science, I agree. But there is no requirement to put the same amount of gas in the tank every time.

Yes, actually, it does. The amount of gas you purchase as measured by the pump, in and of itself, is NOT a true measure of what you burned off since the last fillup. The only way you can calculate a true (and consistent) MPG is by knowing how much gas you took OUT, divided into your miles. Silly example: say I ride 50 miles and only squirt in a tenth of a gallon, does that really mean I can brag on my 500 MPG?? Of course not. You need to know the true consumption.

The ONLY way to know the true amount of gas burned since your last fill-up is to refill it to a consistent level each and every time. Then, and only then, does the pump tell you what you really used since last time. As mentioned by all the good people above, the ring in the filler neck is the best indicator the Buddy has.

TVB · Post by **TVB** » Sun Jan 01, 2012 3:53 pm

pugbuddy wrote:
getting consistent results from tankful to tankful requires that you fill the tank to exactly the same level every time
No, it doesn't. It only requires that you know how much gas you put into the tank every time, which is measured for you at the pump. When you divide by the mileage ridden, that gives you the mpg for that tank.

Suppose I have a full 1-gallon tank of gas, then ride 100 miles. I stop to refuel with only drops left in the tank. But I'm in a hurry, so I'm a bit careless, and only put 0.9 gallons in. Do the math, and I come up with 100 miles on 0.9 gallons: just over 111 mpg. Woot!

I then ride another 80 miles. This time there's some gas left in the tank, so there's only room for me to add 0.9 gallons. But that works out to less than 89 mpg! WTF!

The next time I fill up it's after another 100 miles, and the tank is nearly empty. I fill it to 1 gallon exactly, for 100 mpg.

However, if you average those three rides together, I have a combined distance of 280 miles on 2.8 gallons. I've been getting 100 mpg all along, but I couldn't see that because I didn't exactly fill the tank one time. Now, if I'd known before I refueled each time exactly how much gas was left in the tank, I could've used that information to correct each calculation. But that's impossible to measure, so we rely on averaging over several fill-ups to compensate for that.

pugbuddy · Post by **pugbuddy** » Sun Jan 01, 2012 4:10 pm

Motorcycles (and scooters, I would assume) do vary a lot more than cars. Still, SOMETHING different happened between the time it was getting consistent mileage and what it's doing now.

Exactly. The pattern changed quite a lot, from getting 90+mpg regularly to varying from 65 to 90 mpg regularly (and in a consistent pattern). I can only guess that the highway riding to my new job is affecting it, although I don't know why it would do so in such a huge manner.

Incidentally, it's a 125, not a 170.

Skootz Kabootz · Post by **Skootz Kabootz** » Sun Jan 01, 2012 5:28 pm

pugbuddy wrote:I can only guess that the highway riding to my new job is affecting it, although I don't know why it would do so in such a huge manner.

My MPG went from ~76mpg to ~62mpg when i started commuting. (I ride pretty aggressively on the commute. Generally WOT, stopped, or lane splitting. Plus a few mile stretch of 55+mph, half of it steep uphill) But IMO the decline is because I am in need of an oil change and new rollers. MPG always goes south when that is needed. I'll be doing a service next weekend. I'm curious to see the difference it makes.

Southerner · Post by **Southerner** » Sun Jan 01, 2012 11:50 pm

Oil change I understand, but how often must one change the rollers?

Skootz Kabootz · Post by **Skootz Kabootz** » Mon Jan 02, 2012 3:34 am

Southerner wrote:Oil change I understand, but how often must one change the rollers?

It varies depending on ones riding habits but I believe about every 5-6K is average.

michelle_7728 · Post by **michelle_7728** » Tue Jan 03, 2012 6:36 am

pugbuddy wrote:
getting consistent results from tankful to tankful requires that you fill the tank to exactly the same level every time
No, it doesn't. It only requires that you know how much gas you put into the tank every time, which is measured for you at the pump. When you divide by the mileage ridden, that gives you the mpg for that tank. It's not rocket science, I agree. But there is no requirement to put the same amount of gas in the tank every time.

The other part is that this is a recent phenomenon. As recently as early 2011 my gas mileage was consistently in the 90 mpg+ range. There were no "dips" (over 3-5 mpg) in the mileage at all. Now I'm seeing variances of 20-30 mpg on a regular basis. That change doesn't make much sense to me.

Lots of things can make milage vary - uphill, downhill, prevailing wind direction, temperature, correct tire inflation... mine varies constantly. It is your average mpg that is telling of fuel performance.
Mine is varying--quite consistently--up to 20+ mpg. Since my riding habits are consistent (not perfectly so, of course, but they don't vary that much), I'm not certain why there is such a huge variance in mpg. And it's like clockwork--the first fillup of the week is in the mid-to-high 60s; the second in the mid-to-high 70s; the third in the 90s. I'll probably never know for sure but it's one of those things that suddenly turns up and makes me go "What the heck?".

A couple years back, during the winter, I was having hideous gas mileage in my 2004 Corolla. (This was before I had my Buddy

). At that time, I'm guessing the Corolla had around 30,000 miles on it, as it's around 44K now. Anyhow, I didn't drive any differently, or go on any long, or shorter, trips, didn't get a tune up or oil change during that time frame, and the tire pressure was fine as well. I put it down the the gas I was putting in the car...even though it was always the same gas station(s). Literally, it lasted for the winter that way, then never did it again.