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Why do motorcycles have low fuel economy?

Dirty fuel - ethanol fuel economy

Why do most motorcycles have fuel economy no better than many light diesel and even petrol cars despite being a lot lighter and smaller?

It’s a question that some riders are posing, while many others simply don’t care; they just twist the wrist and revel in the aural delights of burning fossil fuels!

And that’s one of the reasons why motorcycles are not very fuel economical. Most riders simply don’t care. They don’t buy a motorcycle for economy, but for thrills.

Speed record holder Glenn Curtiss on his 1907 V8 motorcycle fuel economy
Speed record holder Glenn Curtis on his 1907 V8 motorcycle

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However, governments around the world are starting to demand improved fuel economy and emissions from motorcycles and that’s not as easy a task for the engineers as you might think.

There are two major hurdles to improving fuel economy from a motorcycle: Aerodynamics and weight.


The most aerodynamic motorcycles have fairings, which are becoming less “fashionable”. Sales of faired sports bikes are on the wane, while there is growth in cruisers, naked bikes and adventure bikes which are not faired.

The most aerodynamically “slippery” motorcycle is the Suzuki Hayabusa which has a drag coefficient (cD) of about 0.55 to 0.60.Suzuki Hayabusa sportsbike fuel economy

Drag coefficient is the ratio of drag on the body moving through the air to the product of the velocity and the surface area of the body.

Even a Mazda6 sedan has a much better cD of 0.26.

Jeromy Moore, Porsche racing engineer and former race engineer for V8 Supercar star Craig Lowndes, says it is difficult for motorcycles to match a car’s aerodynamics, because they are too short.

“With aero, it will be hard to get a bike’s cD down as it is quite short so the air has to deflect at larger angles to go around and rejoin,” he says.

Fuel economy
Jeromy Moore

“Also, of course, it’s not as smooth as a car’s external surfaces with the rider’s body and the fairing trying to deflect air away.”

Jeromy says the Hayabusa doesn’t have half the aero, or twice the drag, as a Mazda6 because cD also takes into account the frontal area blocking the air.

“So if a bike has around a 1/3 of the frontal area then it has 2/3 of the drag force at the same speed,” he says.

“You could actually calculate back a lot from the top speed values given by the bikes compared to the power. If a bike needs 200hp to reach 300km/h and a 911 needs 400hp then you can see the cD times the area is approximately half for that bike than a 911.

“So the next question is, for less drag, why does a bike use more fuel? The engine simply isn’t as efficient at that load. Cars are judged much more heavily on fuel consumption. They aren’t trying to get 200hp per litre.”

Jeromy Moore fuel economy
Jeromy at work


The other hurdle is weight; not just the bike’s weight, but the rider’s.

Jeromy says that weight is an important factor in his job where every 1okg in weight costs them half a second per lap at Le Mans. That’s just 1.1% of an 875kg Porsche 919 Hybrid race car.

A 70kg driver represents just 8% of the combined racer/car weight.

A similarly slight 70kg rider adds a massive 35% to the gross vehicle mass of a 200kg motorcycle.

Fuel economy
Porsche Le Mans race car

Jeromy says weight has the biggest impact on fuel economy around town.

“In terms of the effect of mass on fuel consumption it depends on the duty cycle,” He says. “That is, at constant speed on the highway more weight has an almost negligible effect due to an increase in rolling resistance of the tyres.

“But when you consider the city cycle it has a big effect as you are putting energy into accelerating the weight then when you brake that energy is wasted as it is converted to heat in the brakes (unless you have a hybrid/electric car with regenerative braking!).”


While riders continue to demand high-performance bikes, mostly without a fairing, the answer to better fuel economy lies in forced induction in smaller-capacity and therefore lighter engines.

Kawasaki and Suzuki have both suggested their future motorcycles will include turbo and supercharged engines.

2016 Kawasaki Ninja H2R supercharged
Supercharged Kawasaki Ninja H2R

Other answers are reducing motorcycle weight with new materials and riders going on a diet!

  1. I bought a Honda Forza 250 its better than my old Daihatsu Applause 4cyl from $20 every 3 days to do a 20+min drive to $20 a fortnight is a fantastic saving with the traffic time cut as added bonus. My next bike is going to be a Honda vfr1200fd..

  2. From experience the sole reason for lower fuel economy is this. EPA emission laws. Its a fascicle joke. At the cost of the consumers.
    Lucky for me, the brand of motorcycle I ride, can easily and cheaply (and with half a brain) remedied from this ridiculous situation. I have successfully remapped the ECU, more power, smoother power, cooler running temps and WHAT, a by product of all this, better fuel economy.

  3. Another reason economy is not at the forefront of most commuting riders minds is the cost comparison compared to using public transport or driving.
    My CBR500r uses $10-12 of premium fuel per week for my 35km round trip too and from work each day, with the benefit of free city centre parking.
    Compared to the $8 per day cost of the train for a return journey (plus petrol to and from the station), or at least twice the petrol cost of running my (4 cyl, 2.0l) car on the same journey, plus parking costs for the city of $13-15 per day,
    I’d much rather see motorcycle companies ploughing their R&D money into lighter components and safety than squeezing those last few litres per km out of the tank.

  4. I think another part of the answer might be rpm.

    When I drive my (manual transmission) car I tend to drive in the range of 2,000 to 3,500 rpm for 99% of the time. But most bikes would be spending their time in the 5,000 – to 8,000 rpm range and therefore they have to be using a lot more fuel to go the same distance.

    A case in point is Honda’s super fuel efficient NC700/750 that gets around 3.5l/100km from a 750cc but they hit the rev limiter at around 6,000 rpm and are usually ridden on their torque at much lower rpm.

    1. Most car engines are designed based on the operating principles of truck and other industrial engines, motorcycle engines are based on the principles of race engines. Light weight high horsepower little torque. That has been the formula for the majority of bike engines the Honda Goldwing boxer engines are about the only exception to this rule that aren’t thumping great V twins.
      Forced induction of a bike engine won’t improve things that much without a total shift in the design of the whole system so that the engines have more torque to start with then the gearing can be setup to reduce rpm and fuel consumption .
      It’s a funny thing but unlike cars where a smaller engine usually means better economy on a bike it can be the opposite because a smaller bike will have to rev harder to do the same work and will be at high revs for a lot longer and more often than a bigger engine.

      1. Hmm interesting… but how come the most fuel efficient bikes are the smaller capacity ones like 110-125cc?

        Why isn’t there a 1000cc bike that can match the fuel economy of a 110-125cc bike?

        1. A 1.8 liter vtwin can get 50mpg @ 80mph and 35mpg in the city.
          A 125cc bike can get 85mpg in the city and 30mph at 80mph.
          Most fuel efficient engine depends on the task.

  5. diesel would be the go something like an st1100 style tourer with twice the
    range or an adventure bike with the added bonus of carrying spare fuel
    without risking turning into a human fireball

  6. We like performance in our bikes. If economy is so important, bikes like the Enfield 350cc diesel would be popular outside of India.
    After lane-splitting to the front of a line of cars at a stop light, it is nice to have the acceleration to stay ahead of the cars.
    Diesel does have some potential. There has been ongoing civilian interest in the US Marines M1030M1 diesel bike which is based on the evergreen Kawasaki KLR650, itself a bike that numerous adventure riders have been taking to heart since 1987.

  7. I used to get 32 km/L from my old XL250RC and RF. The Honda CB250RS often got ~35 km/L or better. In the years since mileage has gone down while technology has improved. In India many of the 100-125’s they’re selling get 85 km/L or better. Here similar bikes only get 35-45 km/L.

    They’re using things like swirl induction to improve fuel efficiency.

    We could improve the fuel efficiency significantly on most bikes if we applied some of these same concepts?

    Fuel injection, better spark, better air induction, better filtration, better spark plugs, higher voltages, lighter bikes, cleaner emissions, more efficient transmissions, better lubrication, better steels, improved tolerances, etc… are all capable of improving fuel efficiency. Certainly aerodynamics is not where the extra efficiency is coming from in most countries?

    Aerodynamics are not as important on bikes that only ever do 60 km/h around the city?
    In any case it should still be possible to do stuff with min-fairings to smooth airflow without relying on lots of extra plastic?


    1. I remember riding a friend’s Honda CB250RS back when those bikes were current. Micheal’s fuel consumption is close to what I recorded at the time of about 90mpg (about 3L/100km in the new money).
      Those Indian bikes all have spindly forks and front drum brakes. Surely a Honda CT110 (aka postie bike) can match them?

    2. Sorry Michael, I do have to strongly disagree on one of your points, Cleaner emissions, does not equal better economy. The EPA’s around the world have been striving to achieve so called cleaner emissions, by forcing manufactures to achieve a complete burn. Yet this does not and can not achieve the best efficient consumption.

        1. Wikipedia also shows that increased fuel efficiency and reduced emissions go hand in hand with fuel injection:

          Environmental benefits[edit]
          Fuel injection generally increases engine fuel efficiency. With the improved cylinder-to-cylinder fuel distribution of multi-point fuel injection, less fuel is needed for the same power output (when cylinder-to-cylinder distribution varies significantly, some cylinders receive excess fuel as a side effect of ensuring that all cylinders receive sufficient fuel).

          Exhaust emissions are cleaner because the more precise and accurate fuel metering reduces the concentration of toxic combustion byproducts leaving the engine. The more consistent and predictable composition of the exhaust makes emissions control devices such as catalytic converters more effective and easier to design.

  8. I would be surprised if every designer who looked at the aero dynamics of a bike from the point of view of a plane or a car as that is where all their education focused.
    Now if they looked at it the same way the inventor of the dimples on a golf ball did we might see some really slippery bikes.

  9. Really good article Mark.

    But it still feels weird that my Passat diesel wagon gets better fuel economy than my 2005 BMW R1200GS.

  10. I’ve been riding my NC700sa Honda every day since I bought it in August 2012. I run it on 91 octane and every fourth fill is 98 octane. The bike averages 3.2 litres per 100 kilometres and using 98 octane does not seem to make a difference to the consumption. I’m very happy with this great little runner using it for the daily commute of 400 kilometres per week and regular two up jaunts into the country towns around Perth. I’m currently planning a trip to Sydney and will be on the trusty NC.

    1. Why use 98 octane on 4th fill? Higher octane neither yields better fuel economy nor better power output. It is purely to prevent pre-ignition knock in higher compression engines. Waste of money if you don’t need it.

      1. People read octane numbers wrong. Vehicles are built differently, and are built for certain fuels. Standard cars are built for 91 octane, and function perfectly happily on it. They could achieve a marginal increase on performance on 98, but this is minuscule and not worth the price increase. High performance cars are built for 98. If you give them 91, they die.

        Look at it this way. If you were to get an elite athletic’s food, your performance wouldn’t increase (unless your diet is like 61 octane shocking). But an athlete would suffer terribly on a normal person’s healthy diet.

  11. It is hard to relate to this article because i seem to be the antithesis of “riders”. 8 years ago i went looking for an efficient motorcycle and the BMW F650GS topped the list. At 60+ MPG it turned out to be enjoyable and reliable in many other ways. It also sold well throughout its history, but didn’t provide the “thing” PR people were apparently looking for and has gradually been replaced by the less remarkable 800GS twin. I’m still commuting on my 650 to a job where i drive a fuel economy ‘champion’ Prius around all day- The 650 always gets better mileage despite all of the carbon expended in building the Prius batteries, with enough torque to wheelie from a stop and do 115MPH loaded with luggage. It just won’t ever do the things that make for good magazine articles…

  12. Blame the Motor Racing Federation for it. The fuel efficiency of bikes can easily be doubled by making them more aerodynamic. The problem is the bikes are then getting too fast for the track. So since the 1950s they banned the streamlining of motorcycles. This also had its effects on street bikes, because a lot of motorbike buyers are idiots in jeans that would like to go at least 500 km/h or >300 mph on the motorway. So out of safety they’re very poorly streamlined. Maybe this will change with the electric motorbike, because the max. acceleration and top speed can be regulated very well electronically, but time will tell.

  13. So a 1000cc that makes 150hp and goes 17kml is not efficient for you? A 650 70hp that makes 25kml is not efficient?
    If a 1000 would have 50hp it would be doing 30kml, but sue that motorcycles are born around competitions and a motor with high revs is more easy to handle than a torque one. Also what you read about cars they fuel economy is never matching my car and my bike have the same power, but my bike can reach 16kml and it’s a naked and I’m 190×100.
    Motorcycle motors are very efficient! But we have to enjoy them!! Lamps

  14. Read your article and then the comments , now left wondering if this article is just not an apology to condition bike users to expect poor economy.
    I have always been expected bikes have better economy yet my MV Agusta gives at best 5l/100km , compare this with my Audi V6 3l turbo diesel which returns 6.5L/100km and the Audi given its size is way ahead on efficiency.
    So why the poor performance? Could it be the Motorcycle manufacturers are just lazy and don’t develop their engines , forced injection may be a part of this , however regular car engines which don’t have turbo gear have been around for years and they have very spectacularly achieved better economy.
    It would appear to me manufacturers just focus on bigger and bigger engine capacity for horse power , how ridiculous is an 1800cc cycle engine when many small cars have 1500 and 1600 engines , which by the way return better economy. Manufacturers have been lazy and negligent and self indulgent by expecting their customers to tolerate a big failure.
    The motor cycle media are also at fault because they never seriously examine fuel economy , or the overall economics of running a motor cycle , which then might make buyers more discerning in their purchase

  15. I believe all bikes should have cruise control. This would increase fuel efficiency, safety and less speeding fines.

    1. Bulltish, they constantly lower speed limits and put signs where they are hard to see. It is all revenue raising and NOTHING to do with safety. Otherwise it would be ten times harder to get a license.

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