Behold, The Ultimate Fuel Gauge Has Been Found


This collection of interconnected computation devices that stores humanity’s precious supply of kitten GIFs and naked photos of ourselves and provides the means for strangers to argue with one another via short, bitter paragraphs that we call “the inter-net” is actually pretty useful for other things as well. Things like being introduced to truly remarkable fuel gauges that defy all logic and reason and, as a result, transcend our normal, filthy plane of existence. Fuel gauges like the one seen in this Reddit post.

Confusingly, this post suggests that the fuel gauge “does a pretty bad job at telling how much fuel there is,” when in fact it does a spectacular job, and it’s our failings as humans that prevent us from knowing what the hell it’s trying to tell us:

Wow, right? It’s incredible. Maybe even sublime. As some of the commenters have pointed out, while the little illustration on the dash seems like it could be a riding lawnmower, it’s not. No, this is something much more exciting: a road-roller.


Specifically, this seems to be a Hamm HD Compactline series of road roller, and we can get a good look at the fuel gauge in context of the whole dash in this well-illustrated brochure:

Lovely, isn’t it? Interestingly, the company appears to be using the word “intuitive” in a context I’ve never been exposed to before.

This fuel gauge is absolutely fascinating. I’m a firm believer that fuel gauges are ripe places for exploration and improvement – consider the remarkable Nissan 280ZX’s fuel gauge that included a separate sub-gauge just for the last quarter tank. That’s an incredible innovation.

Nissan’s extra sub-gauge is a clever expansion of the fundamental fuel gauge concept, but what Hamm is doing is more of a deep re-thinking: Why make a fuel gauge immediately understandable when you can make it complex and obtuse? Let’s look at it again:

For a little picture and three labeled LEDs, there’s just so much there. We have three yellowish-green LEDs, labeled 2/3, 1/3, and 1/10. Now, all three are illuminated in this picture, but the real-world picture from the Reddit post just shows the top one illuminated. So, let’s say that’s how it actually works, and this gauge tells you if you have 2/3 of a tank, 1/3, or 1/10.

So, it doesn’t ever tell you if you’re actually full or empty, like some conventional boring-ass gauge. This gauge chooses the path of fractions, but, incredibly, somehow doesn’t use a common fucking denominator for all three fractional values chosen.

Why is that? Maybe because the company arbitrarily decided to divide the tank into conceptual thirds, then found itself written into a corner when it made its middle level just 1/3, and then had nowhere to go?
I mean, Hamm couldn’t even do something that was, you know, a multiple of a third? The 1/10 couldn’t have been, like, 2/9 or something? Then you make 2/3 into 6/8 and 1/3 to 3/9, and at least you’d have a common denominator. I mean, that wouldn’t have been much better, I guess.

But why thirds? Why couldn’t this have been, say, 3/4, 2/4, and 1/4? Did the idea of quarters just feel too, I don’t know, wrong? Shit, if we’re going this way, why not F, 1/2, and E, like any sane human being would do?

What information are you getting out of this madness-inspiring 2/3-1/3-1/10 trio? The sobering realization that no matter how hard you try, you can never have a completely full tank? Or do they just want people re-doing 5th grade math as they try to find the lowest common denominator between 1/3 and 1/10?

What would that be, anyway? 30? So this could maybe have been 20/30, 10/30, and, 3/30? Is that any better? I mean, kinda, because at least we can all accept that somehow this fuel tank is 30 units large?
What is the actual size of the tank? Let’s check the Hamm site:

So, it’s 8.7 gpm. Wait, gpm? That’s gallons per minute! That’s a rate, not a capacity? Shit, now I’m even more confused. What kind of weird sadists run this Hamm operation, anyway?

Even if we assume that’s a typo and it’s an 8.7 gallon tank, that still doesn’t really explain this choice of markings. So, full is 2/3 of 8.7? So, uh, 5.8 gallons? And when you’re at this gauge’s equivalent of empty it’s 0.87 of a gallon?

Any Hamm owners/drivers out there want to help me understand this? In the real world, I’d like to bet that people just use this as a full/half/empty kind of thing.

Still, hats off to Hamm for not being kowtowed into fuel-gauge homogenity! May all of your gauges read 2/3, forever!

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71 Responses

  1. Makes sense. The three lights essentially boil down to:

    -Plenty of fuel
    -Time to find out where the fuel truck is (I assume these things don’t just head for the nearest gas station to refuel)
    -Go directly to fuel truck, do not pass Go

    Kind of similar to the way some cars had a separate gauge for the last 1/8 of a tank since that’s when you really need to know in detail how much is left.

      1. I would like to hear from an operator. It seems to be overly complicated for a simple job. Human Interface 101 – give meaningful data in an expected and easy to use format.

        Boring Fuel gauge -> F to E with markings showing how far to each. Easy to understand.

        Lights of Huh? -> How much fuel? Who knows just run it until stops or break out the calculator and have the foreman yell at you for wasting time.

        1. As a construction worker, we frequently get no gauge at all and also we can’t all be trusted to pay attention to something as nuanced and subjective as an analog dial. “Super says if this one comes on stop and get diesel” is about right. We’re not all idiots, but, well.

          1. Haha! Not a construction worker, but growing up our farm tractors fuel gauges were all broken. Even on the pretty new Duetz Fahr, that stopped working within a couple of years. On the two ancient fords you just banged the tank with a stick that let you know that either you had diesel or you didn’t.

            1. Same farm stuff for me. If you knock on the tank and remain doubtful, just grab the oil dipstick, clean it on your pants and check fuel level accurately.
              By the way, the dipstick could be used to start the tractors (old ones) in case you forgot the keys.

              1. I’ve heard that the dipstick in the Renault 4 can be used to start it, but never tested that myself. Sometime ago someone broke into mine (front doors don’t lock, so maybe “entered” is a better description that “broke into”); there was nothing of value inside the car so they went for the engine compartment, which has a special “trick” to unlock. They were unsuccessful in opening the hood, but they were very successful in bending both corners. I couldn’t figure out what they could possibly want from inside the hood, and when I shared this with my local Quatrelle community lots of people commented that they were after the dipstick to start the car and steal it.

  2. Agree with some of the above, even in a road vehicle Full and Empty aren’t a lot of use.
    Aside from the aforementioned lending scenario, when does anyone need to know their vehicle is more than 2/3 full.
    Empty is also useless, car stops = empty, nearly empty though makes sence.

  3. Are we sure it only illumiates 1 LED at a time? In my mind it would be a great gauge if it started unlit for full, then added the other lights as supply diminished. A fully lit set (preferably with 1/10 being red instead if yellow) would be a clear warning.

  4. You know they say that all gas gauges are created equal, but you look at Hamm and you look at other cars and you can see that statement is not true. See, normally if you go one on one with another gas gauge, you got a 50/50 chance of a full tank of gas. But I’m a gas gauge freak and I’m not normal! So you got a 25%, AT BEST, at full. Then you add a few LED lights to the mix, your chances of a full tank of gas drastic go down. See on a regular gas gauge, you got a 33 1/3 chance of still having gas, but I, I got a 66 and 2/3 chance of a full, because your gas gauge KNOWS it can’t beat me and it’s not even gonna try!

    So, you take your 33 1/3 of a TANK, minus my 25% of a tank and you got an 8 1/3 chance of still having gas. But then you take my 75% chance of a full tank, if we was to go fill up today, and then add 66 2/3 per cents, I got 141 2/3 chance of a full tank of gas. See , the numbers don’t lie, and they spell disaster for you at the gas pump.

      1. Or the pre 1930 ‘dipstick and a can on the running board’ method.
        Some early Citroen s had a petrol tank over the engine mounted to the bulkhead, simple gravity feed to the carburetor, and a glass tube with a red marker inside protruding from the scuttle. A piece of wire went into the tank, marker on the top, cork on the bottom et voila, une jauge à essence.

      1. The horn button on construction equipment is always an icon of a bugle, when it isn’t a generic button crudely screwed into the dash with a hand-written label saying “Horn!” next to it.


        When you push the horn button, the vengeful spirit of Miles Davis is summoned to unleash his wrath upon the unbelievers.

        Don’t they teach *anything* in school these days? Sheesh.

  5. I kinda get it. Seems to me the key is that this is professionally-maintained equipment for a very specific, bounded purpose?

    If you’re operating it, you don’t need to know that it’s completely full (compared to say loaning your Camaro to your uncle on the promise he’ll return it full), you just need to have a sense of if you can complete whatever the job is you’re doing.

    Fraction choices aside, seems it could have said “plenty of fuel”, “some fuel”, and “refuel soon”?

    I’m not in the business, but I don’t think these things travel great distances on their own where a more detailed gauge would be useful. Don’t they usually get picked up by flatbeds when they need transport? I’ve never seen one at a gas station (but willing to bet someone here has).

  6. What if each lamp is to be taken as cumulative?
    Full tank – 2/3 & 1/3 lit
    99% -> 78% – 2/3 and 1/10 illuminated
    77% -> 68% – Just the top bulb.
    Nothing lit? Get the can!

    You get the idea from there.

    Does it work that way? No idea. Should it? Yeah, why not. 8 levels from 3 bulbs.

  7. Logical thing would be an analogue needle. Cheap thing is lights.

    Full light is useless, it’s hardly ever full.

    Empty light is useless, you have already run out of fuel

    So you have three lights:

    More than 2/3 of a tank

    More than 1/3 of a tank but less than 2/3 of a tank.

    Not quite empty, but we sell this in 20 countries and Reserve isn’t standards compliant world wide.

    You know that joke about the German taking the car back to the dealership because the fuel gage said empty and the car was still running? I know that guy. I bet this is a German brand.

  8. Is it me or is the main improvement to a gas gauge to be made is linearity. That is, the first half of a tank of gas lasts twice as long (or so) as the second half tank of gas according to the gauge. “Twice as long” is obviously arbitrary but you get the idea. The gas gauge seems to linger in the top half longer than the bottom half.

  9. I think 1/10th remaining is a much more interesting thing to know than 1/3. Who fills up with 1/3 of a tank left?!

    Anyway, this is yet another of many areas where presentation has warped people’s expectations of the capabilities of the underlying thing. You gas gauge has a highly damped needle that gives you the impression the sender has specific, detailed knowledge of how much fuel you have. And the DTE number further expands the legend of what is actually a crude device.

    This is the same as the “controller vs. mouse” debate in video games. Controllers are made out of garbage components. Their resolution is low. The output varies significantly from component to component…. Whereas mice are high resolution and precise. But we paper over the shortcomings of the controller in software to make the user _think_ that the controller is precise and accurate and that their skill is properly conveyed to the machine, when in reality it’s all bullshit.

    Anyway, IMO the correct solution to this problem is to replace fuel senders with devices that measure the mass of the remaining fuel rather than a crude float that bobs and weaves with your suspension and slope of the road and all of the rippling after effects thereof. If we can put accelerometers in microchips – and clearly we CAN – this is something we can get done.

  10. I wonder if this gives info in a very particular way , intended for a typical working day?
    For example 2/3 means it’ll last ’till lunch break, 1/3 means it will only last ’till morning tea, while 1/10 means stop work now and fill .
    In a way thats better than a normal gauge where you’d need to know fuel consumption rates.On a jobsite where any Joe will be using it, that would make things super simple

  11. When was the last time any of us saw a needle gage actually track in a linear response to fuel level? They stay stuck on full until the first quarter tank is burned, race down to 1/4 indicated when there’s a third left, and say they’re empty with around 20% fuel remaining. Temperature gages are even worse liars. Automakers don’t think we can handle the truth.

  12. We had a large old tractor at my grandfather’s farm. Unlike this piece of construction equipment, it did not have industrial grade mechanical vibrators built in.

    Yet any time the tractor was running, the needle of the fuel gauge would vibrate rapidly and violently enough to become a blur between E and F. It didn’t matter how much fuel was in the tractor; if it was running, there was simply no way of knowing.

    A Hamm’s gauge would have been a great improvement.

  13. Incidentally, “gallons per minute” thing is probably literally true. In a lot of construction equipment the engine is only there to power the hydraulic pump, and as such has fuel consumption that is basically constant. It’s much more like a generator than a car engine, a given quantity of fuel will produce a predictable duration of runtime regardless of how far the machine physically moves.

  14. I work in a rental yard for a local heavy equipment dealer and see all sorts of weird fuel gauges. It is amazing across one line of equipment has so many different styles of gauges. And don’t get me started on where the fuel fillers are.

  15. Torch:
    You get all spun up around the concept of a common denominator (9), then throw us a curve by turning 2/3 into 6/8. You’re flustered, and it shows.
    AND: is “homogenity” a word? (I’m guessing you’re looking for “homogeneity”.)

  16. That is absolutely brilliant, the gas guage alone is amazing.

    2/3 — don’t worry about it. Plenty of gas.

    1/3 — time to fill the tank, no panic.

    1/10 — head directly to fill now, panic.

    It’s FULL when you FILL IT. If you just filled it, you know this, why does the guage need to tell you? You know you have plenty of gas.

    It’s not a speedo or a tach, it’s not a gauge you stare at while driving (flattening wily coyotes, whatever). It’s a reference to “hey, how we doin over there?”.

    As a thought experiment I like to reduce instrument design to and beyond functional minimum. Here, one RGB LED could do it:

    2/3 green
    1/3 yellow
    1/10 red


  17. If you look at the lower right hand side of the control panel, it appears there are some vibratory settings for the roller drums. At least, that’s how I interpret the sinusoidal waves. If you’re setting up that much vibration in the system, maybe a needle gauge is no longer useful.

  18. I figured it out. Googled the company.

    “Hamm AG is a German worldwide manufacturer and marketer of road rollers based in Tirschenreuth, Germany.”

    They’re German! Why use three bolts when eight will do? Why have a simple, easy to read gauge that doesn’t require solving a math problem to understand? Because this is BETTER. Why? Well… We haven’t exactly decided yet. But it is. Trust us. We’re German engineers.

    I bet you have to disassemble the entire machine to check the oil.

    1. I fucking hope not, it’s an OSHA violation to not check the oil at the beginning of every workday and make a note in the log book. Not that that always gets done, but it should at least be possible! Every machine I’ve dealt with has big hatches that expose all the guts and the dipstick is right there.

  19. To build on what others said, 2/3 is for first thing in the morning; it means “fill the tank on the way to the jobsite” (or before leaving the yard if there’s a refueling setup there, which I suspect is often the case).

    1/3 is “you probably have enough fuel to finish the day out if it’s close to quitting time anyway.”

    1/’10 is “you have just enough fuel to get this loaded on the truck under its’ own power, so stop rolling right away.”

    Likely the only time you ever see all three lit at the same time is a test phase upon startup.

  20. Thank you for “road roller”. It has always bugged me that the only word I knew for those things was “steamroller” when they presumably haven’t run on steam for over a century.

    As for the fuel gauge, I am wondering if all three lights turn off when it’s full. That would at least make the 2/3 light mean something … but then what happens if the gauge stops working???

  21. Funny thing is I don’t pay attention to the gas gauge on my car anymore. It’s new enough that it has a little carputer built into the dash that shows miles to empty, and that’s what I go by. It’s also got the yellow “2 gallons left” warning light.

  22. You know it’s full because you are putting the fuel in and you stop just when it starts spilling over. It’s not as in a car, where you can’t see [censored], here you are looking straight into the fuel tank 🙂

    The lights… it’s realy wrong if it’s one diode at a time, it’s much more intuitive when its “three dots… two dots… one dot… action” or better “no action” 🙂

  23. Jason, that’s a 280ZX gas gage, not a 280z!
    The 280z, the last of the s30 z’s, had a traditional gas gage.
    The 280ZX, the s130, had the double gage. The s130 was the change from sports to GT car.

  24. I think it is a combination of work environment & menstruation.

    You need lights & not a gauge because anything glass fronted will crack on Day 1.

    You can’t have very sensitive fuel gauges – these, I am sure , jounce around quite a bit. So the sensitivity of the sensor itself has to be low.

    Couple it with what is likely to be a shallow, broad fuel tank, you probably cannot reliably measure how much is left.

    So idiot lights saying “Fine”, “Fret” & “Fill” probably work best

  25. I actually like the light thing. No point in a “3/3” light, because after you filled up, it would go out when you started the car. I’m not necessarily defending the particular segmentation into 2/3, 1/3, panic (probably makes sense for the current application) but the concept is reasonable. I don’t care if it’s precisely 1.4 gallons left, it’s panic time! (my light seems to come on somewhere around 20%). Don’t want to let it get down to the bottom, so you won’t fry the fuel pump. It’s not like my gas gauge reads in gallons in any case. It would save a wee bit in manufacturing cost over a physical needle. And if it’s being done on a screen, it’s not really analog anyhow.

    1. “No point in a “3/3” light”
      You say that, but this same company (Hamm) makes a soil compactor with a fuel gauge that reads 1/1, 1/2, and 0. These Germans can’t make up their minds about how they want to measure fuel!

      As for this road roller, here is what the manual says about the fuel gauge: “The fuel tank filling level is displayed by an illuminated pilot light. According to the filling level, the luminous point moves between 2/3, 1/3 and 1/10. If the level drops below 1/10 the luminous point flashes. Refuelling is necessary!”

  26. I assume that this works this way because of the shape of the gas tank and/or using switches instead of a single float. Probably can’t set up a very accurate single float and don’t really need to know anything more precise.

    1. In my experience the gas tank on machines like this is most often a semi-transparent cube of polyethylene. The “gauge” is when you squint at the filthy plastic and try to decide if you can wait until tomorrow before putting in more diesel or not.

  27. OK, so I don’t operate a *lot* of construction equipment but I do get involved with it from time to time—mostly telehandlers, boom lifts, and scissor lifts. Anyway, that fuel gauge is actually perfectly appropriate (and is anyway a big improvement over the “open the engine hatch and squint at the polyethylene fuel tank” system that is all you often get) in this application, and here’s why:

    Nobody on a construction site gives a shit about how much fuel the equipment has in it. At least, surprisingly few people seem to. If you’re lucky you have a service that comes by the jobsite every few nights and fills everything up for you, but a lot of the time it’s a matter of jerry cans full of diesel and since nobody wants to have to deal with that and it’s nobody’s actual job to deal with it, it frequently doesn’t get done often enough. With everything typically running on diesel fuel, you can see why that’s a problem.

    What construction workers need is an idiot light that tells them if they have most of a tank, some of a tank, or almost no fuel left. That’s what this gauge provides! There’s no need to have a stupid fucking passive-aggressive argument about whose job it is to fill the machine and why aren’t the jerry cans full and whose turn was it to do that and is the needle really at 1/4 or what and does or does not the machine totally have enough fuel for a couple more days, and on and on. The site super can just say that when the 1/3 light comes on the machine should get refueled at the next lunch break, and if the 1/10 light comes on the operator should stop immediately and refuel the machine or else. No arguments, easy breezy (beautiful Covergirl).

    It’s actually surprisingly brilliant and I wish it were more common. It would be terrible in a car, but I love it for a jobsite.

    1. From the land of sky blue waters….. Hamm’s the beer refreshing….
      We used to swipe Hamm’s from my buddy’s dad when we were kids. It was almost a treat when he’d splurge on Oly. Oly was nasty, but better than Hamm’s.

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