[fuel_addict]

Why is this such a big deal when the end result is the same? Its purely a matter of convenience. Neither kpl nor lit/100km is better than the other. One would use what one is conversant with. In most cases, it would be kpl. Car manufacturers and users always specify mileage in kpl. lit/100km involves that extra bit of calculation. I would stick to the Indian standard of kpl.

[alpha1]

The thread actually makes a lot of sense.

KPL does not give you how much will be your fuel cost.
That is given by litre per km. (x rupees/litre)

Which is inverse of kpl.
Which also means that the difference in kpl figures makes sense only in the beginning (say a jump from 5 to 6) but is insignificant at higher end (say 20 to 22)

Ppl have tendency to evuluate using a linear scale - which is not the reality. And that is what the thread is all about.

[anilisanil]

Title of thread is misleading, how do you mean "which is better?"

Ultimately it is the same car, same kilometers and same liters changing the way one sits on the other does not change anything else. If a car returns 10KM per liter it consumes 10 liters for 100Kms.

Mathematics is reality, it does not change itself when we change the way we calculate it.

[sgiitk]

Litres /100km is the norm in Europe. See the VW 3l car (it meant that it consumed under 3litres per 100km!)

[anshul_UVA]

I think that L/km is a measure that should be kept in mind when comparing vehicles, specially in different vehicle classes. For example, for someone in the market for a huge truck, the mileage range for which are 10-15 kmpl, a 15 kmpl vehicle saves 33% fuel over the 10 kmpl one. Thats a big jump and could be detrimental in the purchase. On the other hand, if someone wants to but vehicles in the 25-30 kmpl range (not practical today, but later maybe), the difference in the fuel costs between 30 kmpl and 25 kmpl is about 16.6%.

Adding another dimension to this, from an auto OEM perspective. We rave about the ultra high fuel efficient vehicles giving 40 mpg (hybrids in the US). Is the incremental fuel efficiency as beneficial, when compared to a 35 mpg vehicle?

So, from a business perspective which makes more sense?
a) improving the efficiency of a high mpg vehicle (which is already close to the ceiling and thus involves higher costs), going from 35 mpg to 40 mpg.
b) Improving the efficiency of a big truck or van (which might be an easier task and might be less costly), going from 10 to 15 mpg which would bring about much more fuel saving.

For me, this question is better answered in the l/km unit.

[manishk83]

Originally Posted by Pri2

I am not saying that they are any different, they are exactly the same thing, but when it comes to understanding fuel economy, I feel liters /100 kms gives you the better picture.

As someone has already pointed out on this thread, here is an example:

Say you have an old Indica that gives you a FE of 15 and you decide to upgrade to a Indica Vista that gives you a FE of 20 KMPL. The FE gain here is more than upgrading from a Vista (20 KMPL) to the 25 KMPL Indica.
Though you can see that the FE increment is just 5 kmpl. For a person who calculates in KMPL the gain will seem to be same > 10kmpl - 15kmpl - 20 kmpl but for someone who calculates in liters / 100 kmpl the gain is : 3.33 liters - 1.67 liters - 1 liter.

I agree that we have grown up following KMPL hence it easier for us to understand it, but if you look logically, liters / 100 kms gives you a better picture on FE and that's my point.

I agree and was actually very surprised at the numbers that came out of looking at lts/100 kms rather than kmpl. I was watching at this new Indica ad on TV, where the lady kept gushing on the 25 kmpl fuel efficiency. And I was like wow! 20kmpl which is the norm in diesel cars, to a car which now gives 25 kmpl. That's amazing!

Looking at the calculations in Pri2's first post, it's actually an incremental saving of only 1 litre for every 100 kms, or 40 paise/ km (diesel at Rs 40/lt).

I have read other's replies saying that 10-15 kmpl is 50% improvement and 20-25 kmpl is only 25% increment, so the lt/100 km improvement should be obvious. But frankly, to me this wasn't as obvious until I looked at Pri2's post. Some how one tends to put more weightage on "5 kmpl ka improvement hai" rather than "sirf 25% better mileage hai".

I think looking at lt/100 kms lets you put things in a better perspective when calculating your potential savings.

[Ragul]

I think kmpl units is useful when purchasing a car and not having experienced driving it - it tells us how much the running cost is going to be.

However once you are driving it, worrying about every kilometer you extract from it per liter, as you drive - is like being a Neurotic with an endlessly worrying habit. It serves no purpose. It is more sensible to think in terms of how much petrol you need for the next 100kms * X (where X is the multiplier for total trip distance planned) to estimate the cost of the trip - or in terms of ltrs/100km.


Then again, if you find mileage to be unsatisfactorily low, the communication with the garage service mechanic becomes vague if you tell him - "I have to fill in 3 liters for every 100kms". That communication is best said this way - "The car is giving me only 10kmpl in city, please do something to improve it".

So while one unit of measurement (ltrs/100km or kmpl) can be extrapolated from the other, it is important to switch the mode of measurement mentally depending on the context and communication required.

Just my chaar aanas.

--Ragul

[rajchetan]

I think KMPL is the better way.

Every rupee saved is a rupee earned. Its better and easier to compare the cost per KM using KMPL.

Note:- even if the difference between Car 2 & Car 3 is not much, there is still a difference and its a rupee saved. Which is why we calculate KMPL right? Paisa Vasual.

[Suess]

I think it is the way we take things: kmpl is for economic minds and l/100km is for fuel efficent minds.

we don't care about litres, we care about how much it will cost us! in Europe it's about fuel efficeny, environment etc. so, they care how many litres they are buring for 100km!

[ashphil]

Whichever way we calculate the answer is not going to change. I think it is all a matter of what we have got used to and what our perspective is.
I remember the old mechanic's way of calculating fuel consumption by filling a graded bottle with 250 ml petrol, feeding it direct to the carb and then driving/ riding on watching the mileage run by until the vehicle ran out of gas. That allowed us to calculate KPL.
Today I drive a Chevy caprice V8 (in Saudia! Where else?) and am most comfortable when at the press of a button the dials show me how many more kms I can travel with the petrol left in my tank. Still, KPL any day! A matter of perspective, I guess.
Regards,
Ashok

[dustom_99]

Well kmpl or ltr/100 or any other is just as suitable if one did not bunk school a little too often.specially class 6th and 7th. This debate would not suit even school kids!
What really imprsd me is that even on this topic almost everyone has a viewpoint. Hail democracy!

[Dr.AD]

Although I agree that the conversion between these two units is trivial and hence it does not make a big difference which one is used, I still prefer km/l.

The reason is that I like the denominator in any scientific unit to be a 'unit'. That is, I would prefer liter/km (I know this would sound crazy) over liter/100km (which I believe is a flawed unit because you can't have a denominator of 100 units). Since in km/l the denominator is a unit (i.e. 1 liter), it is a technically correct unit and hence I prefer this.

[bigautobuff]

liters/100kms i think is better suited to highways or long distance runs..literally speaking it is just catching your nose straight away or by wrapping your hand around your neck and then catching it...So whatever you are comfortable with should be used..