[Pri2]

Countries like India and US measure fuel economy by KMPL or MPG and European countries measure it by Liters / 100 kilometers. I have gone through some articles on this topic and based on my understanding, Liters/100 kilometers represents fuel economy better than KMPL.

Here is a table I created:


If you look at the above table, Even though there is just a gap of 5 kmpl between each cars, You save 3.3 liters for 100 km if you switch from a car that gives you 10 KMPL to a car that gives you 15kmpl, and only 1.7 liters if you switch from a car that gives you 15 kmpl to a car that gives 20 kmpl.


Here are some interesting articles on this topic.

A video from New Scientist:

YouTube - ‪'Miles per gallon' can misrepresent a car's fuel efficiency‬‏

An article from Popular Mechanics.
Why We Should Measure by Gallons per Mile, Not Miles per Gallon - Popular Mechanics


What do you guys think? Which method of measuring fuel economy is better? Should we continue with KMPL or switch to Liters/ 100 Kms?

[MadTiger]

Hi Pri2 really nice thread. This really gives me a different perspective towards calculating fuel economy. What surprises me more when I go through your chart, the car that give 10 kmpl vs 15 kmpl has a considerable amount difference in fuel consumption whereas the same between 15 kmpl and 20 kmpl is quite less. If I had to calculate just like that, in would have assumed the car with 20 kmpl more efficient and cost effective. This is really a nice way to understand consumption vs economy. Good thread !

[dhanushs]

IMO, liters/100kms are better suited to highways or long distance runs, and vice versa.

[androdev]

IMO, kmpl is better because its easier to get a sense of rupees per KM. It's same as other popular units like mpg.

[DieselFan]

Nice thread. lts/100 kms is always better representation for cash savings or fuel savings or Carbon emission reduction calculations. even if you use KMPL to carry out above calculation one has to convert to lts/100 kms. or lts/1000 kms.

[vina]

What's the difference? the conversion from one to the other can be done mentally by anybody within a 5% accuracy, and by many within better than 1%.

[subscrive]

Originally Posted by MadTiger

Hi Pri2 really nice thread. This really gives me a different perspective towards calculating fuel economy. What surprises me more when I go through your chart, the car that give 10 kmpl vs 15 kmpl has a considerable amount difference in fuel consumption whereas the same between 15 kmpl and 20 kmpl is quite less. If I had to calculate just like that, in would have assumed the car with 20 kmpl more efficient and cost effective. This is really a nice way to understand consumption vs economy. Good thread !

Of course a 20kmpl is more fuel eff!
10 to 15kmpl is 50% increase. 15 to 20kmpl is NOT 50% increase.
So better to go for 25kmpl indica than 35kmpl nano (futuristic diesel kmpl projection of nano for example sake).
Its the matter of getting used to the units.
Hope you are now clear.

[alto99]

Figures in last column are flawed. It should be either liters / 10000km or the figures should be divided by 10.
1000liters/1000km would mean 1kmpl

[bluevolt]

KMPL is better because it is easy to read and understand whereas liters/100 km is bit confusing especially when reading from MID while driving. I prefer KMPL. Many cars do have liters/100 kms reading style like in Fortuner. KMPL reading would be updated frequently while this is not same for liters/100 KM method.

[Fordmanchau]

Originally Posted by vina

What's the difference? the conversion from one to the other can be done mentally by anybody within a 5% accuracy, and by many within better than 1%.

Originally Posted by subscrive

Of course a 20kmpl is more fuel eff!
10 to 15kmpl is 50% increase. 15 to 20kmpl is NOT 50% increase.
Its the matter of getting used to the units.
Hope you are now clear.

Originally Posted by alto99

Figures in last column are flawed. It should be either liters / 10000km or the figures should be divided by 10.
1000liters/1000km would mean 1kmpl

Quoting three replies which best describes all my observation about the first post in the thread.
It's not so complicated to convert units first of all. Besides being a standard, you have a freedom to follow your own unit for your personal usage.
And yes the figures in the last column is wrong.Divide all those by 10 and then you'll have the correct figure.

[sgiitk]

I think it is a matter of perspective. Litres/100km is the long standing European method, and I see the logic in it. The more economical the vehicle the lower the figure.

I must say I often covert the consumption to mpg for my own understanding so old habits die hard. Hence, this km/litre which is a fall-back on mpg!

[Pri2]

Originally Posted by alto99

Figures in last column are flawed. It should be either liters / 10000km or the figures should be divided by 10.
1000liters/1000km would mean 1kmpl

My bad, the last column heading is supposed to be liters/ 10,000 kilometers.

[libranof1987]

Originally Posted by alto99

Figures in last column are flawed. It should be either liters / 10000km or the figures should be divided by 10.
1000liters/1000km would mean 1kmpl

Was wondering about the same until I realized it was a typo!

Originally Posted by sgiitk

I think it is a matter of perspective. Litres/100km is the long standing European method, and I see the logic in it. The more economical the vehicle the lower the figure.

I think more than perspective, it is a matter of generalization.

Consider this : A car runs some distance and the owner calculates the FE. The owner might have calculated it for very short distances; say full tank at odo 30000 and the next full tank at 30060. The car could have run either completely on the highway, or thru' the city or thru' heavy traffic.

While, if you calculate FE over a broader range i.e. 100kms, there is a possibility it could cover distances when the car was driven at steady speeds in combination with other road conditions.

So, the litres/100 kms would just give a broader picture.

FE cannot increase between the 2 calculations; it is just depends on the base factor.

[vina]

Originally Posted by libranof1987

Was wondering about the same until I realized it was a typo!



I think more than perspective, it is a matter of generalization.

Consider this : A car runs some distance and the owner calculates the FE. The owner might have calculated it for very short distances; say full tank at odo 30000 and the next full tank at 30060. The car could have run either completely on the highway, or thru' the city or thru' heavy traffic.

While, if you calculate FE over a broader range i.e. 100kms, there is a possibility it could cover distances when the car was driven at steady speeds in combination with other road conditions.

So, the litres/100 kms would just give a broader picture.

FE cannot increase between the 2 calculations; it is just depends on the base factor.

Wouldn't ltr/1000km be a better bet going by your logic?

Many people driver more than 100km within city over the week and then similar numbers on the highways on the weekends - their calculations will get flawed too.

It is pretty straight forward to do basic mathematical operations like averaging, taking a reciprocal and multiplying/diving by roughly 2.5 (or 4) - whic is what mpg to kmpl entails (roughly) - almost all old time shopkeepers do that in their head and there is no reason why others can not do it with reasonable accuracy.


I think this whole debate it more pointless than even diesel vs. petrol (generic comparison) debate

[dhanushs]

Originally Posted by vina

I think this whole debate it more pointless than even diesel vs. petrol (generic comparison) debate

True, just a matter of perception. Take whichever is comfortable for oneself.


But then, Fuel Efficiency generally is a measure of efficiency. So, the output/unit fuel consumed would be the correct form of expression.

If we take the example of a generator, the FE is KW/liter, similarly some machines have hours/liter, so for a car or a locomotive, whose sole purpose is transportation, distance/ unit fuel consumed should be the correct way.

In India its Kms/Liter, and in US its Miles/Gallon