Fuel efficiency and Litre / 100km calculation

drivedrive72

Hi folks,
Trying to figureout the Litre / 100km calculation for two cars, tocompare, which is the more fuel efficient.
Any idea where online I can figure out this information?
Reason being when I use the AA roadwatch planner, I can enter the priceof petrol, for a litre, but I am at a loss to figure out what the litre per1000 kilometres figure is for each car.
I’m trying to compare a 1998 Starlet with a 2000 Vauxhall Corsa?
Does anyone know in general how they might contrast?
Thanks

Max Power1

Use MPG (you could look it up online on honest john)
...
...
profit?

Leonard Hofstadter

Indeed, what's wrong with using mpg? Cars like that will have the clocks in miles anyway, so you only have to convert litres to gallons (divide by 4.5 if my memory serves me correctly). I'm all for doing things in the metric system, we're not as backward as the Brits on that after all, but litres/100 km is the most meaningless unit of measurement I've ever come across! Why isn't it kilometres per litre?

againstthetide

Google is your friend:

https://www.google.com/search?q=what+is+9.5+litres+per+100+kms+in+mpg

Using 9.5 as that's what my car was reporting yesterday evening

Yakuza

captainspeed wrote: »

Indeed, what's wrong with using mpg? Cars like that will have the clocks in miles anyway, so you only have to convert litres to gallons (divide by 4.5 if my memory serves me correctly). I'm all for doing things in the metric system, we're not as backward as the Brits on that after all, but litres/100 km is the most meaningless unit of measurement I've ever come across! Why isn't it kilometres per litre?

A higher l/100km reading means more fuel used = less efficient. Fairly intuitive, but no less so than a lower MPG = less efficient. Horses for courses.

The accurate conversion figure is to divide the figure you want to convert into 282.3 (4.544 * 100 / 1.609344) and that that gives the value in the opposite system, but 280 is easier to do and is reasonably accurate.

Eg :
30 MPG ~= 280/30 = 9.3 l/100km
40 MPG ~= 280/40 = 7.0 l/100km
50 MPG ~= 280/50 = 5.6 l/100km

6 l/100km ~= 280/6 = 46.7 MPG
8 l/100km ~= 280/8 = 35 MPG

againstthetide wrote: »

Google is your friend:



https://www.google.com/search?q=what+is+9.5+litres+per+100+kms+in+mpg



Using 9.5 as that's what my car was reporting yesterday evening

^^^ Be careful with google - that particular calculator uses US gallons which are different to Imperial!!! 1 US gallon is roughly 5/6 of an Imperial gallon

drivedrive72

Thanks for the feedback folks, think I got sorted.

againstthetide

https://www.google.com/search?q=what+is+9.5+liters+per+100+kms+in+miles+per+imperial+gallon

Good Call Yakuza!

Shakti

http://www.fuel-economy.co.uk/calc.shtml

alias no.9

captainspeed wrote: »

Indeed, what's wrong with using mpg? Cars like that will have the clocks in miles anyway, so you only have to convert litres to gallons (divide by 4.5 if my memory serves me correctly). I'm all for doing things in the metric system, we're not as backward as the Brits on that after all, but litres/100 km is the most meaningless unit of measurement I've ever come across! Why isn't it kilometres per litre?

l/100km is a measure of consumption, you use x litres to travel 100km

km/l would be efficiency, you can travel x km for every litre

Two related parameters with very different political angles, one is almost destructive in its tone while the other is kind of empowering. The shift to the destructive term didn't happen by accident.

Just Jack

againstthetide wrote: »

Google is your friend:

https://www.google.com/search?q=what+is+9.5+litres+per+100+kms+in+mpg

Using 9.5 as that's what my car was reporting yesterday evening

if you go there, you are only getting 24 mpg, I went to the next link and got 30 mpg for my 9.5, I think 30 is more realistic

puzzle factory

jesus fup, my pajero is doing 14mpg.

eqwjewoiujqorj

alias no.9 wrote: »

l/100km is a measure of consumption, you use x litres to travel 100km

km/l would be efficiency, you can travel x km for every litre

Two related parameters with very different political angles,
one is almost destructive in its tone while the other is kind of empowering.

The shift to the destructive term didn't happen by accident.

Could you explain this in more simpler terms for those of us down at the back of the class.

againstthetide

Just Jack wrote: »

if you go there, you are only getting 24 mpg, I went to the next link and got 30 mpg for my 9.5, I think 30 is more realistic

Yep my second link uses imperial gallons and not us gallons

Leonard Hofstadter

So in other words, unless you're an absolute genius or have Google with you at all times, it's impossible to convert from l/100 km to mpg!

If we used km per litre for metric I would have changed years ago to metric for fuel consumption, speeds and distances are in kms and we buy fuel by the litre.

But since I grew up learning mpg, I'm still using it as l/100 km is too complicated. And there's no point in becoming familiar with km per litre since it's not used here, which I think is a pity.

againstthetide

The metric system is the tool of the devil! My car gets 40 rods to the hogshead and that's the way I likes it.

RED PASSION

againstthetide wrote: »

The metric system is the tool of the devil! My car gets 40 rods to the hogshead and that's the way I likes it.

ahhhh it is a prius with those figures

againstthetide

RED PASSION wrote: »

ahhhh it is a prius with those figures

More like a hummer
From wiki
This is approximately 0.002 mpg, 10.5 feet per gallon, or 0.8 meters per liter). 40 rods make one furlong, so 8 hogsheads are needed for one mile

RED PASSION

againstthetide wrote: »

More like a hummer
From wiki
This is approximately 0.002 mpg, 10.5 feet per gallon, or 0.8 meters per liter). 40 rods make one furlong, so 8 hogsheads are needed for one mile

Of course, of course, i was sick the day they did this in school :D:D

The Pontiac

How accurate are these trip computers?

Last 2 days I'm getting 5.2 liters to 100km, which works out at 54mpg. Don't believe that for a second. Some main road driving, a bit through the city, and some b roads. 1.9tid Saab. I'd expect more like 45mpg tbh. I reckon it's a liar!

Jellicoe

<Ollie> wrote: »

How accurate are these trip computers?

Last 2 days I'm getting 5.2 liters to 100km, which works out at 54mpg. Don't believe that for a second. Some main road driving, a bit through the city, and some b roads. 1.9tid Saab. I'd expect more like 45mpg tbh. I reckon it's a liar!

In my experience, they are only a guide and often an optimistic one. You need to check em against several real life manual measurements of brimming the tank, doing several hundred miles and brimming the tank again to work it out accurately.

The Pontiac

Jellicoe wrote: »

In my experience, they are only a guide and often an optimistic one. You need to check em against several real life manual measurements of brimming the tank, doing several hundred miles and brimming the tank again to work it out accurately.

I was actually planning on doing that, but laziness got the better of me.

Yakuza

alias no.9 wrote: »

l/100km is a measure of consumption, you use x litres to travel 100km

km/l would be efficiency, you can travel x km for every litre

Two related parameters with very different political angles, one is almost destructive in its tone while the other is kind of empowering. The shift to the destructive term didn't happen by accident.

That's one perspective, I guess, albeit a little cynical

Knowing your car's L/100km facilitates some calculations, like knowing how much fuel a particular trip is going to use (and cost) and (assuming you know your fuel tank's capacity), what proportion of the tank it's going to use as you only have to multiply numbers (and the only division is by 100 which is easy) eg:

I've got to do 300 km on the motorway, my (petrol) car gets 7 l/100km on motorways so it'll take approx 21 litres which will cost approx €35 and use 1/3 of my 65l tank.
or:
I've got to do 186 miles on the motorway, my (petrol) car gets 40 MPG on motorways so it'll take approx *runs off, finds calculator* 186/40 = 4.65 gallons which is approx *tappety tap* 4.65 * 4.544 = 21 litres which will cost approx €35 and use 1/3 of my 65l tank.

I know which of the above set of calulations I'd prefer to do!

IMHO l/100km has only really come to the fore here since we went metric with speeds in 2005, as manufacturers left metric as the default measurements of the trip computers in their cars since we'd shed the baggage of Imperial measurements. I still can, if I ever feel the need, change my car to tell me the MPG, but meh.

I've been going to and from Spain for over 20 years, and as far back as I can remember, TV ads for cars there always specified l/100km as the fuel consumption, not km/l, so showing l/100km is not a recent thing worldwide, just here.

mickdw

<Ollie> wrote: »

How accurate are these trip computers!

They can be accurate or way out depending on the car. I know mine (and most VW/Audi) can be adjusted via vagcom to give lower or higher values by basically adding a correction factor as required.

Leonard Hofstadter

mickdw wrote: »

They can be accurate or way out depending on the car. I know mine (and most VW/Audi) can be adjusted via vagcom to give lower or higher values by basically adding a correction factor as required.

One of the cars I had used to tell me it was doing 20% better than it really was:D!

My current bus often reports back that it is doing ever so slightly less mpg than it really is, happy days:)! It's actually one of the most accurate trip computers I've ever come across to be honest.

spr1nt3r

drivedrive72 wrote: »

Hi folks,
Trying to figureout the Litre / 100km calculation for two cars, tocompare, which is the more fuel efficient.
Any idea where online I can figure out this information?
Reason being when I use the AA roadwatch planner, I can enter the priceof petrol, for a litre, but I am at a loss to figure out what the litre per1000 kilometres figure is for each car.
I’m trying to compare a 1998 Starlet with a 2000 Vauxhall Corsa?
Does anyone know in general how they might contrast?
Thanks

Best method to accurately measure the consumption of your car is:
1) Fill the tank all the way to the top (2-3 clicks)
2) Reset the trip meter
3) Drive until your fuel is as low as you can get it (drive as you would normally, don't rev high etc.)
4) Refill the tank all the way to the top (2-3 clicks)
5) Calculate - 100 / (trip_meter / litres_to_fill) that will show liters per 100km
note: if your clock is in miles formula is - 100 / (trip_meter x 1.6 / litres_to_fill)
/ stands for divide x stands for multiply

Leonard Hofstadter

spr1nt3r wrote: »

Best method to accurately measure the consumption of your car is:
1) Fill the tank all the way to the top (2-3 clicks)
2) Reset the trip meter
3) Drive until your fuel is as low as you can get it (drive as you would normally, don't rev high etc.)
4) Refill the tank all the way to the top (2-3 clicks)
5) Calculate - 100 / (trip_meter / litres_to_fill) that will show liters per 100km
note: if your clock is in miles formula is - 100 / (trip_meter x 1.6 / litres_to_fill)
/ stands for divide x stands for multiply

Or, if you have a car with the clocks in miles, do steps 1-4 as above and for step 5), simply divide the number of miles by the number of litres consumed, and then multiply your answer by 4.546, much easier:)!

Matt Simis

alias no.9 wrote: »

l/100km is a measure of consumption, you use x litres to travel 100km

km/l would be efficiency, you can travel x km for every litre

Two related parameters with very different political angles, one is almost destructive in its tone while the other is kind of empowering. The shift to the destructive term didn't happen by accident.

Yep, well explained!