Why are bikes not fuel efficient?

[Magnum]

OK, this may be a silly question, i don't know and i do not yet own a bike.

Why is it that my family diesel people carrier can do a quoted "57mpg" whereas the bike i want to get only does 49mpg.
Most bikes are around this sort of level.

I would have thought that a motorbike having a very small engine in comparison to a car, and a fraction of the weight, it should do many more miles to the gallon?

Am i getting confused here or are motorbikes not that fuel efficient?

[Silver]

[Robby]

The engines are designed to make power, not to be efficient.

Simple thing up front. To make 100hp, you need 100hp's worth of fuel and air. So based on that, you could roughly assume a 600cc sportsbike to deliver similar fuel burn to a 1.6l petrol hatchback.

Then there are engine, particularly cylinder head, efficiencies. Bike cylinder heads operate at high rpm, and therefore are optimised for this. This means getting as fuel and air in as possible. In cars the push is to burning the fuel completely, no maximum throughput.

Also, until just a few years ago, a lot of bikes were air cooled and carbed. Now fuel injection is standard across big stuff, and water cooling is used more than it was. This increases efficiency, but in bikes efficiency is just used to make more power.

Aerodynamics are a factor, bikes don't really have them.

The way in which they are driven/ridden. If you ride your bike like someone would drive a car, expect better fuel burn.

Real versus quote figures. That 57mpg quote car does 40, maybe 45mpg in real life.

Of course, cars are also dragging a lot more weight around, but the basic idea is that cars are tuned towards efficiency, and bikes towards outright power.

I still want my 150kg, 100mph, 150mpg bike.

[Charlie]

They haven't (in the recent past) been designed to be that efficient, that wasn't the selling point of motorbikes. It is only recently that people have become obsessed with efficiency.

If you want an efficient bike take a look at diesel bikes.
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Past: Honda x8rs, Honda City fly, Honda Hornet 250, Honda VFR750, Yamaha xt600e.
Current: Honda CBR929RR & Yamaha XT660Z Tenere

[Kickstart]

[The Shaggy D.A.]

[JonB]

I know people say you can never meet the manufacturers figures for MPG. But I constantly beat my manufacturer.

On Paper the Citroen C1 should return a combined average of 61.4MPG. I am consistently returning 64MPG. That's a mixture of motorways, city driving and general pissing about.

Petrol has just dropped to 89.9p a litre at morrisons here, 20 odd quid is getting me 420 miles to a tank at the moment, it's a little bit odd.
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Be careful whose advice you buy, but, be patient with those who supply it. Advice is a form of nostalgia, dispensing it is a way of fishing the past from the disposal, wiping it off, painting over the ugly parts and recycling it for more than it?s worth.

[neil.]

4 stroke 125cc bikes like the CG and YBR can do 90-100mpg...
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CBT February 2008 | A2 June 2008 | Yamaha YBR125 (written off) | Honda CBF125 (current)

[Irezumi aka Reuben]

Quite possible to get 50mpg+ out of a 600 sports if ridden sensibly. Even if driven sensibly something like a Subaru Impreza wouldnt get anywhere near that. Using the Impreza as a vehicle with relatively close acceleration and top speed.

Something like a Deauville can do 65mpg easily.

[Dalemac]

[paulcdb]

my mr2 = 30mpg max

my cbr600 = 50-60mpg depending on riding, twice as fast, better for overtaking...

won't complain at my bike doing 50+
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Excersise is rubbish!
If your healthy you don't need it... if your sick you shouldn't do it.

[iooi]

[rotax81]

stick a big person on your roof and dangle a couple of single mattresses out the side windows then see if it does 57 mpg

my audi tdi does a regular 46mpg - max 125mph
my 636 worst consumption is 32mpg - MIN 125mph
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ZX636C6F road. ZX636C1H track. ZX7R redundant. ZX0.5R minimoto as ornament.
Audi A4 Avant 1.9TDi and VW Transporter 2.5TDi 888 Special (no mot and tax lol)