Metric Fuel Consumption

[Vanin]

I know that the subject is a little tired but buying a Japanese import Volvo has made me think again on the subject

Nobody I know quotes their car's fuel consumption in Litres per 100 km. Not only that but most people, even younger "metric minded" people do not even know the measurement let alone the figures for their car.

All the road signs are in miles and all the fuel pumps are in litres.

The Volvo has a readout in Kilometres per litre which is far more sensible as it becomes more accurate as the car becomes more frugal

The difference between 1 litre/100km and 2 litres/100km is about 140 miles per gallon so you are into meaningless fractions for a realistic comparison.

How on earth did the Europeans adopt such a stupid system and why did they not do km/litre like the Japanese?

[thinkofaname]

If the difference between 1 litre/100km and 2 litres/100km is about 140 miles per gallon, then the fractions aren't "meaningless."
Likewise, kilometres per litre only "becomes more accurate as the car becomes more frugal" if you restrict yourself to whole numbers.

Seems like you just don't like decimal points. In terms of significant digits, 3.2 L/100km is no better or worse than 32 km/L.

[mybrainhurts]

Because not kamikaze...

[thelawnet1]

Vanin said:

I know that the subject is a little tired but buying a Japanese import Volvo has made me think again on the subject

Nobody I know quotes their car's fuel consumption in Litres per 100 km. Not only that but most people, even younger "metric minded" people do not even know the measurement let alone the figures for their car.

All the road signs are in miles and all the fuel pumps are in litres.

The Volvo has a readout in Kilometres per litre which is far more sensible as it becomes more accurate as the car becomes more frugal

The difference between 1 litre/100km and 2 litres/100km is about 140 miles per gallon so you are into meaningless fractions for a realistic comparison.

How on earth did the Europeans adopt such a stupid system and why did they not do km/litre like the Japanese?

You are completely wrong.

Firstly, actual car real mpg ranges from, high of say 60mpg to a low of say 15mpg.

This works out as 4.7 to 18.8 litres per 100/km.

So your example of 1 litre versus 2 litres per 100 km is irrelevant because cars use much more fuel than that.

Secondly, although the fractions aren't meaningless, they aren't as important as all that, because mpg varies hugely depending on driving route and style.

So saying 60mpg = 5l/100km and 15mpg = 19l/100km actually works just fine.

Thirdly, distance per mile (e.g. mpg) is the wrong way round. Example: I do 20,000 miles a year and have a vehicle that does 20mpg. That's ~£5,500 in fuel. If I trade it in for a car that does 30mpg (10mpg better), then the bill falls to ~£3,667, a saving of £1833 or 33%

However if I have a car that does 50mpg, then my fuel bill is £2,200. Trading it in for a vehicle that does 60mpg (10mpg better) only cuts the bill to £1833, that's a saving of only £367, or 17%.

By contrast the comparable l/100km:

Example 1: 15l/100km or 10l/100km
Example 2: 6l/100km or 5l/100km

Much easier to see that the first comparison is from 15 litres down to 10 litres, that's a saving of 5 litres, whereas the second example you only save 1 litre.

You put litres of fuel in your car, so it's easy to calculate.

A real world example is that Mercedes say for the C-Class:

C63: 34 mpg
C43: 35 mpg
C200: 51mpg
C200d: 65mpg
C220d: 67mpg
C250d: 63mpg

These figures in l/100km:

C63: 8.3
C43: 8.1
C200: 5.5
C200d: 4.3
C220d: 4.2
C250d: 4.5

The litres/100km are easier to read, and see the real difference between C63 and C200 is much bigger than between C200 and C220d, say.
and the decimal point is hardly scary - you could do it as l/1000km if you wanted, and make it 55l vs 43l, no difference from having 51mpg vs 65mpg in terms of the number of significant figures.

To make it more obvious that you are completely wrong, let's ask how you calculate the cost of owning/driving a car, or taking a taxi ride. Do you calculate pence per mile or miles per pence? It's obviously pence per mile. And what 'litres' and 'gallons' really represent is money. E.g., if petrol is £1/litre, then you can write '£ per 100km instead of litres per 100km'. Whereas if fuel was £1/gallon, then it would be £(1/mpg) per mile.

The correct unit in this country would actually be litres/100 miles, since we use litres for fuel and miles for distance.

Gallons are completely gone.

Edited by thelawnet1 on Wednesday 22 November 01:42

[Mr Tidy]

[quote=thelawnet1]

You are completely wrong.

This works out as 4.7 to 18.8 litres per 100/km.

What a load of nonsense - 4.7 what to 18.8 litres per 100km? Bananas to apples, or carrots?

[TooMany2cvs]

In a lot of ways, fuel-used-for-given-distance makes a lot more sense than distance-per-unit-fuel.

I want to go from here to there, how much fuel will I need? All you then need to know is how much fuel costs per unit, and you know how much it'll cost.

Distance-per-unit-fuel doesn't really tell you anything useful until you turn it around.

But it's what our heads are used to in this country, so the alternative simply feels unfamiliar.

It's just another example of how ridiculous this whole clinging to Dibnah units is. EVERYWHERE in the world, bar one other country, uses the same units and scales. The UK uses units of the same name, but different size, to that one other hold-out country. The UK government's original target date to complete metrication was nearly half a century ago now...

[Dammit]

I had the garage upgrade the onboard computer on my car to show range remaining- grown so used to it on the Volvo that I wanted it on the 996 as well.

It brought with it a litres per 100km display which I find quite handy for the very reasons Mr 2CV mentions.

11l/100km is my average IIRC.

[AndySheff]

Mr Tidy said:

thelawnet1 said:

You are completely wrong.

This works out as 4.7 to 18.8 litres per 100/km.

What a load of nonsense - 4.7 what to 18.8 litres per 100km? Bananas to apples, or carrots?

Made perfect sense to me.
4.7 l/100km, compared to 18.8 l/100km.

[brman]

thelawnet1 said:

The correct unit in this country would actually be litres/100 miles, since we use litres for fuel and miles for distance.

Edited by thelawnet1 on Wednesday 22 November 01:42

Which is what my Mazda indicates. Which confused a lot of people as they assume it is litres/100km

[RHVW]

it is just what people are familiar with. Here in Spain people still think about house prices in pesetas although the euro started 18 years ago.

- after almost ten years of driving here i still convert the litres per 100 kms to miles per gallon. Having said that, I got into the car on the wrongside yesterday after filling up. Surprised there wasnt a steering wheel on the right!

[TooMany2cvs]

RHVW said:

it is just what people are familiar with. Here in Spain people still think about house prices in pesetas although the euro started 18 years ago.

Don't even start the oldiwonks off on shillings... They don't need much excuse.

[Agent XXX]

Guess the car? (official figures)

78 L/100 km

[captain_cynic]

Vanin said:

I know that the subject is a little tired but buying a Japanese import Volvo has made me think again on the subject

Nobody I know quotes their car's fuel consumption in Litres per 100 km. Not only that but most people, even younger "metric minded" people do not even know the measurement let alone the figures for their car.

All the road signs are in miles and all the fuel pumps are in litres.

The Volvo has a readout in Kilometres per litre which is far more sensible as it becomes more accurate as the car becomes more frugal

The difference between 1 litre/100km and 2 litres/100km is about 140 miles per gallon so you are into meaningless fractions for a realistic comparison.

How on earth did the Europeans adopt such a stupid system and why did they not do km/litre like the Japanese?

Just because you don't understand the system does not mean it is stupid.

The L per 100KM is a better system because it's an aggregate of your driving over 100KM, so this would be several days of daily commute for most people. Also, 1L per 100 KM is 282 MPG. That's nowhere near realistic.

My current car is measured to one decimal place for Imperial, if you change it to metric its still measured to one decimal place. 21.8 MPG is 13.0 L/100KM.

To put things in perspective, 70 MPG is 4.0 L/100KM, 40 MPG is 7.0 L/100KM and 10 MPG is 28.7 L/100KM.

To me, maintaining MPG is a daft system as we sell petrol in litres and metric is computationally convenient. At the very least we should be using Litres per Mile.

Edited by captain_cynic on Wednesday 22 November 10:01

[captain_cynic]

Agent XXX said:

Guess the car? (official figures)

78 L/100 km

Challenger 2 or ancient V8 Range Rover?

[cptsideways]

And just to confuse you my two Insights are in KM per L which actually is a much more refined figure.

Eg 100mpg is: 35.2 km/L or 2.82 L/100km


When you have such a frugal vehicle the decimal places matter

[Shakermaker]

thelawnet1 said:

Thirdly, distance per mile (e.g. mpg) is the wrong way round.

I don't know about where you live, but where I live, the distance per mile is a fixed amount

[Vanin]

Well none of you litres/100km geeks have convinced me.
Firstly I do not know anyone or any garage trying to sell cars that quotes anything but MPG.
Secondly most people I ask even the young do not even know the measurement when I ask them. They usually say "Is it kilometres/ litre?"
It is quite strange to have the range remaining quoted in km when all the road signs are in miles.

You do not seem to understand my point about the difference between 1 litre/100km and 2 litres/100km
Yes it is unattainable in the real world but it is something we should strive for and when you have these ultra light, efficient electrically assisted vehicles doing 1000 mpg or more it means something to most people as they can compare it with the 50 mpg of their own vehicle,
1000 mpg is let me find a calculator..........somewhere around 0.25 litres/100km? So you have a competition with these vehicles to see who can be the most frugal one does 1045 mpg and the other does 1057 mpg. You are trying to tell me that the result is clearer in fractions?

Taking on the point about Spanish houses still being sold in pesetas, all the young I know who accuse me of being a Luddite measure their height in feet and inches and their weight in Lbs or stones, their manhood in inches (mm seem so inferior!)
Why do you still sell wine by the dozen everywhere especially in France?

[Krikkit]

So this whole thread is you posing a test case that makes more sense in your preferred unit, then poo-pooing anyone who tries to propose that the real world is better served by L/100km?

Your 1045 vs 1057 mpg case gives 0.267 or 0.270 L/100km, but if you could achieve economy that high you'd revalue the unit - i.e. 26.7 or 27 L/10Mm

[Shakermaker]

It costs me around £60 to fill my car with fuel and that gets me about 400 miles with the type of driving I do, but on a couple of long runs that can go up to 5-600 miles.

That's all that really matters to me.

[captain_cynic]

Vanin said:

Well none of you litres/100km geeks have convinced me.
Firstly I do not know anyone or any garage trying to sell cars that quotes anything but MPG.
Secondly most people I ask even the young do not even know the measurement when I ask them. They usually say "Is it kilometres/ litre?"
It is quite strange to have the range remaining quoted in km when all the road signs are in miles.

You do not seem to understand my point about the difference between 1 litre/100km and 2 litres/100km
Yes it is unattainable in the real world but it is something we should strive for and when you have these ultra light, efficient electrically assisted vehicles doing 1000 mpg or more it means something to most people as they can compare it with the 50 mpg of their own vehicle,
1000 mpg is let me find a calculator..........somewhere around 0.25 litres/100km? So you have a competition with these vehicles to see who can be the most frugal one does 1045 mpg and the other does 1057 mpg. You are trying to tell me that the result is clearer in fractions?

Actually, if you go to any other country, all cars are sold with L per 100 KM (except for countries that are stuck in the past). MPG is a relic of a bygone era. No-one is actually going to miss it.

Also, everyone I speak to knows what L/100KM is, you need to start hanging out with smarter people. You're just behind the times and are angry that no-one else is. Figuring out your real L/100KM by comparing the KM's you did to the amount of fuel you put in your car in your head is dead easy, try doing that when your economy is measured in MPG and your fuel is measured in litres.

Vanin said:

all the young I know who accuse me of being a Luddite measure their height in feet and inches and their weight in Lbs or stones

Not sure what you're on about, I'm 184 CM tall, the last doctor who measured my weight gave it to me in KG (this was in the UK). Seems you're making things up to justify being behind the times.

Vanin said:

Why do you still sell wine by the dozen everywhere especially in France?

Because 12 is easily divisible by 2, 3, 4 and 6. What dozens are bad for are multiplication and orders of magnitude. Who wants to figure out what a dozen, dozen dozens are? So we use a dozen for things we want to equally portion but don't care about multiplying.

Might I save you time on your next post and just give you this to copy:

angry old man yelling as sky said:

I don't understand maths and just want to whinge about things that have changed decades ago.