Confusing fuel mileage

[Hmcp88]

I have to throw an opinion out there about the HUGE inconsistencies with the fuel mileage on this bike. First things first I have never seen such a wide variety of fuel mileage from one bike. Around town things stay pretty level but can still vary up to 10 mpg from my experience. It usually stays the same but sometimes it changes. But that's not my gripe. My gripe is when it drops 20-30 mpg on long travels. So I'll begin my thoughts.

Yesterday and today I rode to and from Orlando for a H-D training class. I had the option of staying in a hotel but I like to ride more (and see my family). Total mileage there and back was 300ish miles. Everything went well (of course) but my fuel mileage stayed the same. By the way it's I-95 and I-4 the whole way so 75-80 mph the whole way. Now by stays the same I mean every fuel up was above 62mpg which I find great for those speeds. You can look at my Fuelly for further details. No complaints on this trip.

The questions I have are why? I have taken longer trips before where multiple fill ups are needed in a day and fuel mileage seems to drop every time I fill up. You can also see those fuel ups on my Fuelly around April 17th to April 25th of this year when I went to Texas. They dropped to 48 mpg at one point and were consistently below 60 mpg. Same speeds, just repetitive back to back fill ups. Same results just not as bad on the Miami trip I took.

Here's the thought I have because I makes no sense any other way, and let me hear what you think if I'm wrong. My thoughts are that this ECM on this bike learns your riding habits and adjusts based on how you are riding? Maybe making adjustments only so many miles? Now this is just theory but I can't logically think of any other reason it should drop only in that situation. How can ride for a whole tank at the same speeds, but if you let the bike rest and do it again later it doesn't affect the mileage? Maybe the bike is adding fuel at those high consistent speeds after some time to help keep the engine cool since you are demanding so much all day?

Sorry for so much writing but this bike confuses me, I think I know what it's going to do just when it switches up on me. Any thoughts other than the bike learning what you want of it and adapting?

Thanks, Matt

 

[dduelin]

The Honda ECU isn't that smart to adjust to rider habits. Perhaps the coolant temperature varies a lot due to sticking thermostat and the resulting rich mixture drops mpg. Without a gauge you wouldn't know the thermostat sticks open only would you notice a closed fault when the engine ran too hot. I have to say I do not notice this variation on my bike. Our mutual friend Jessie at Honda asked me about this behavior and referenced your questions about mpg after your Austin trip.

Edit to add: Wind speed dramatically affects my mileage at higher speeds. My worst mileage has been bucking a stiff headwind and still riding 80. At 80 mph just a ten mph headwind means you are running 90 mph through the air. We have had 10-20 mph southerly and southeasterly afternoon winds. Perhaps?

 

[searsboy]

I think Dave nailed it with the wind factor. Seems like I remember you hitting some pretty stiff wind on the way to Austin.

 

[Jeff762]

It could be the percentage of ethanol in the fuel, at different gas stations. The higher the ethanol level the lower the fuel mileage will be.

 

[Bug Dr.]

My guess would be wind also. DCT or manual? I'm guessing manual.
Mike

 

[Mr_Krabs]

There's also freeway wind tunnel effect. You may not notice it but on much smaller bikes like 150cc bikes you definitely notice. On a freeway with consistently moving traffic you basically get a 5mph "tailwind", basically the draft from all the other cars around you pull you forward and give you about a 5 mph top speed increase. This along with prevailing tailwinds can add up to quite significant variances in mpg especially if you rode straight through in one direction.

Motorcycles are inherently terribly unaerodynamic with drag coefficients of about .6 that's terrible basically a motorcycle is a flying brick. Having such bad aerodynamics means you're far more affected by headwinds and tailwinds in regards to power needed to overcome the wind. Since overall drag increases with the cube of velocity, if you have bad aerodynamics even slight changes in relative wind velocity over the bike add up to much larger variances in total drag force and it only gets worse as velocity is increased as on a freeway. Hence the much more varying fuel consumption especially when on freeways.

 

[anglachel]

Other than just wind another possibility: multiple fill ups in a day at highway speeds suggests highway gas stations... highway gas stations don't always seem to carry the best gas (very few people complain when they are just passing through) ...

 

[danrev]

Maybe you should just stay out of Texas!

 

[mbrown01]

Yes its definately the speed and the wind combined. When I do day trips on two lane very rural highways in north central Wisconsin, I achieve 70-78 mpg. Its a steady cruise of 60 miles an hour 80% of the time the other 20% is slowing to 45 m.p.h. through small towns along the highway. on the interstate cruising at 80 just this last Sunday I only acheived 60 mpg. Its the compromise I can live with. Smaller engine will work harder at these speeds. 60 mpg is still better than anyone else traveling at those speeds.

 

[Hmcp88]

I just thought of this when you mentioned aerodynamics. The one thing that has changed since I went to Texas is the sw motech trax trunk that I now have. I wouldn't have thought this before but maybe the trunk smoothes the wind behind me helping my drag? It may be a square box but it never pushes through the wind, you body and windshield do that part. It just receives wind from around you, which goes around it. Maybe the "tail wind" created by the box is smoother than nothing being there?

 

[670cc]

Other than just wind another possibility: multiple fill ups in a day at highway speeds suggests highway gas stations... highway gas stations don't always seem to carry the best gas (very few people complain when they are just passing through) ...

Not to start a "gas thread", but what could be different about the highway gas vs non-highway gas, that would cause lower gas mileage? Do they add inert fillers?

Greg

 

[showkey]

Do they add inert fillers?

Greg

Nope........they take away the placebo...........


Crap gas is available every where.......

 

[anglachel]

Not to start a "gas thread", but what could be different about the highway gas vs non-highway gas, that would cause lower gas mileage? Do they add inert fillers?

Greg

It may just be my paranoia, but when a proprietor of a sales establishment knows that he will have very little return customers they don't exactly strive for quality, it is amplified even more when they know people won't even bother to complain cause they will be miles away by the time they realize it.
I know these things happen, and at plenty of fast food restaurants you can watch this happen when the "cooks" make a sandwich one way for people who are dining in, and another way for those that are in the drive thru. Believe it or not they some of this stuff down to such a science that they can save money by giving a burger 2 pickles in a drive thru, vs. 3 in the dining room, and receive no complaints.

Highway gas stations do have something going for them though, they usually cycle gas regularly (it isn't left to sit in the tanks for days on end) but they can also have things going against them (tanks get re-filled more often, end up getting stirred up more often ends up with more junk floating in the gas.)
Of course highways are also what we use to cross state lines, and crossing state lines can also be crossing into different additives and % ethanol...

In my experience more often than not when I get a noticeably bad tank of gas it's from gas station right by a highway. I suspect because they can sell it and never hear a word about it... or maybe because when they sell it they don't ever hear about it so they never know that they are selling crap.
I prefer to fill up at gas stations that have populations centers near them, some place where the locals would at least complain when they get a bad tank... But it could just be me being paranoid.

 

[davidc83]

My opinion would be wind, age of gas, gas blends (winter blend versus summer blend-in my jeep I get a much lower mpg average with winter blend than summer blend, and here in Indiana, some of the refineries were still selling winter blend in May), also, since the bike holds less then 4 gallons, the level of the bike when filling up-many gas stations do not have level areas along their pumps, and if the bike is leaning more or less at each fill up, less or more gas is added-even when using the same virtual mark in the gas tank.

 

[Fuzzy]

I just thought of this when you mentioned aerodynamics. The one thing that has changed since I went to Texas is the sw motech trax trunk that I now have. I wouldn't have thought this before but maybe the trunk smoothes the wind behind me helping my drag? It may be a square box but it never pushes through the wind, you body and windshield do that part. It just receives wind from around you, which goes around it. Maybe the "tail wind" created by the box is smoother than nothing being there?

Have you noticed the flaps starting to show up behind semi-trailers around the trailer doors forming a sideways pyramid? They are there to improve airflow and reduce turbulence behind the big rigs which improves gas mileage. How the air comes off the back makes a difference.

 

[mcook]

Just to add my 2 cents, here. I've seen 15+ mpg shifts with wind on my NC. The bike is modestly powered and fairly tall geared, so any time you're running fast and/or fighting wind, you have to dip quite a ways into the throttle. My bet is that the Honda ECU begins going richer at what it perceives as high power settings.

I've noticed a swing in mileage with aero drag (taller windscreen, handguards) as well as with winter fuel.

It's my experience that the NC has bigger swings than most, though you can get a Ninja 300 to really gulp the fuel under the right circumstances.

 

[L.B.S.]

Just to add my 2 cents, here. I've seen 15+ mpg shifts with wind on my NC. The bike is modestly powered and fairly tall geared, so any time you're running fast and/or fighting wind, you have to dip quite a ways into the throttle. My bet is that the Honda ECU begins going richer at what it perceives as high power settings.

I've noticed a swing in mileage with aero drag (taller windscreen, handguards) as well as with winter fuel.

It's my experience that the NC has bigger swings than most, though you can get a Ninja 300 to really gulp the fuel under the right circumstances.

Quite so

I could see mid 20's mpg's in the city with my F800ST, but 68-70 mpg on a gentle highway tank-full distance.

 

[Deleted member 1183]

I had occasion to travel about 350Kms on my NC yesterday. I filled up at the beginning of the spin and at the end of it. I did the calculation on the first tank. It produced 73 Miles per Imperial gallon. The driving for that tank was mixed backroads and various trips on motorways for short distances. I drive briskly, but when on the NC I always short shift and let the bike get up to speed without resorting to full throttle. This style of riding would be in sharp contrast to my 950SM for instance.

The second tank consisted of mainly steady motorway driving at around 130Kph (true speed) . I expected the fuel consumption to worsen but it did not. Again 73 Mpg. I believe the secret is to avoid hard acceleration and allow the bike to get up to speed briskly while short shifting . I rarely rev to more than 4000 rpm on acceleration.

 

[davidc83]

The faster you go, the harder you are on acceleration, the more gas you are going to use. Steady pace, easy on the throttle=better mpg. Same with autos, same with motorcycles.
By the way, most, if not all, gas stations in a geographical area receive their gas shipments from the same refinery, and in the same gas trucks. Trucks pulling into a Marathon station will then pull in a Chevron or Shell station. All the different additives each Station touts as being special, are added in the fuel cells in the gas trucks. Also, getting gas as the station is receiving a shipment has 0 affect on the gas we pump. The station tanks have filters and if you look at the pumps, you can see what looks like oversized oil filters which are in fact fuel filters. The bad gas syndrome is mostly in our heads for us who used to purchase gas in the 60s and 70s, when the pumps and tanks were not regulated by the EPA. We can get water in the gas, but that is usually caused by lots of rain in the area or very humid days, which causes precipitation inside the storage tanks (same as our gas tanks).

 

[TheEdge900]

One more consideration is altitude. On fuel injection engines the effect is two fold. When you are cruising down the highway you don't need maximum power and are using minimal throttle. The fuel injection system only gives enough fuel for the oxygen flowing thru the engine. At higher altitudes you have less oxygen in the air so for a given throttle position you are actually using less fuel.

Secondly at higher altitudes you have less air pressure and your wind resistance is less, therefore improving your fuel economy also. This effect is higher than you think.

Living in AZ and traveling throughout the rockies I have seen my best mileage by far at high altitudes.

Sent from my SCH-I545 using Tapatalk