calculate fuel consumption...........

Submitted: Monday, Feb 03, 2003 at 22:20
ThreadID: 3219 Views:10020 Replies:12 FollowUps:14
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Just a quick question.....why do we use how many litre/100km when we talk about fuel consumption/economy...............
for me, I calculate how many km I have travelled from trip meter and divide it by how many litres I have put.......... say 300km use 35L fuel....then get 8.6km/litre.......so I can accumulate brunch of data and get the statistic thus the average fuel consumption figure..........

But just wonder why we can't use how many km per litre as fuel consumption figure but use how many litre per 100km???????????

so in this way, i know if I put 10 litre from jerry can, I can run proximately 86km.........

Anyone can tell me why ?
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Reply By: Old Soldier - Monday, Feb 03, 2003 at 22:40

Monday, Feb 03, 2003 at 22:40
G'day,

I think it depends on just who you are talking to at the time.

I know people who use l/100km, km/l and old buggers [like me] who still like to work in mpg.

it's all too much for me so I use conversion tables to help me out.

There is a good one at:

http://www.metroyamaha.com.au/tools.htm

It has several intersting conversion calculators and the fuel conversion is down the bottom of the page - just below the fuel consumption calculator

Hope this is of interest

Enjoy the bush

DennisN
AnswerID: 12448

Follow Up By: Tuco69 - Tuesday, Feb 04, 2003 at 00:00

Tuesday, Feb 04, 2003 at 00:00
G'day Old Soldier - I went to the conversion page and found that something doesn't add up!

Given that there are 4.546092 Litres in an Imperial gallon and 1.609344 Kilometres in one Statute mile - then by my maths (questionable accuracy) 4.546092 divided by 1.609344 equals 2.8248106 - which is then used as the conversion factor for MPG/KPL.

So 10KPL should be 28.248106 MPG.

However the conversion page shows that 10KPL is 23.53MPG !!

Working backwards from this, it seems that whoever created the page has used the litres to gallons(US) figure of 3.785411784 incorrectly!

3.785411784 divided by 1.609344 equals 23.521457...

Bit strange using US gallons on an Aussie site!

Tuco in Cairns


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Follow Up By: Iamgq - Tuesday, Feb 04, 2003 at 00:55

Tuesday, Feb 04, 2003 at 00:55
Hi Tuco69!
The Page is correct. If you consider one gallon liquid(US),
it equals to 3.785412 litre..........not 4.546092 litres which is used by UK.
So, as this site probably constructed by American so it use US liquid Gallon.....not UK gallon...
so if you use 3.785412, you will calculate 23.52MPG

here is a very good site for unit conversion http://www.onlineconversion.com/volume.htm

you will be amazed if you know there are so many units are there.
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FollowupID: 7262

Follow Up By: Tuco69 - Tuesday, Feb 04, 2003 at 09:33

Tuesday, Feb 04, 2003 at 09:33
G'day Iamgq,
sorry but I disagree with you!

The site at http://www.metroyamaha.com.au/tools.htm is an AUSTRALIAN site. Note the presence of 'au' in the URL address.

Here in Australia we always used Imperial measurement for liquids prior to when Australia went to metric. All measurements wether they were fluid ounces, pints, quarts or gallons were based on the Imperial gallon.

I worked in the Oil industry at the time Australia went metric. The official conversion factor for gallons to litres was 4.54609 . This is the figure that all Customs and Excise duties are calculated with. A practicle example of this is the 44 gallon drum which became a 200 litre contailer with minor adjustments to dispensing equipment.
44 gallons (IMP) x 4.54609=200.02796 litres

So the AUSTRALIAN page refered to above is NOT correct if it uses the US gallon conversion factor.

Sorry, but thats the facts ...

The site at http://www.onlineconversion.com/volume.htm is an American site and can easily be distinguished as such when they refer to the Imperial gallon as a gallon(UK) and also spell 'litre' as 'liter'.
'Litre' is is spelt using 're' in both the Oxford and Australian dictionaries. American dictionaries spell it with 'er' .

We may have to follow our blind leadership into war with the Americans, but certainly don't need to talk, spell and calculate using their figures!

Tuco
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Follow Up By: Tuco69 - Tuesday, Feb 04, 2003 at 14:19

Tuesday, Feb 04, 2003 at 14:19
As a follow up, I contacted Metro Yamaha and they have now updated the page to include both US and Imperial gallons ...
>

Tuco
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Reply By: ExplorOz Team - David - Monday, Feb 03, 2003 at 23:05

Monday, Feb 03, 2003 at 23:05
We installed both into the Trek Fuel system on this site. Personally I use both however it is easier to calculate kms/l.

Regards
David
AnswerID: 12452

Reply By: Bernie - Monday, Feb 03, 2003 at 23:24

Monday, Feb 03, 2003 at 23:24
I Agree with Old Soldier

another good site for quick conversion of all 3 ways is
www.hicloneqld.com/date.htm

Cheers
AnswerID: 12457

Reply By: Mikef_Patrol - Tuesday, Feb 04, 2003 at 08:24

Tuesday, Feb 04, 2003 at 08:24
Hi IAMGQ

" I calculate how many km I have travelled from trip meter and divide it by how many litres I have put"

Good idea. Km/L is OK. To get L/10KM just divide 100 by your KM/L figure and voila!, L/100KM. (ie 300/35 = 8.571...=KM/L)

To get MPG, multiply your KM/L figure by 4.54 then multiply that answer by 5, then divide that answer by 8. (ie 8.6 * 4.54 = 39.044, 39.044 * 5 = 195.22, 195.22 / 8 = 24.4025 = MPG)

OR

To get MPG, multiply your KM/L figure by 2.8375. (ie 8.6 * 2.8375 = 24.4025 = MPG).

{ 2.8375 is derived from 4.54 * 5 / 8 and is a constant as it is the same in every calculation. The result using the long way and the short way are both the same, well, according to the calculator in XP anyway :):) }

Always carry a calculator in the car nowadays. :)

MikeF
AnswerID: 12464

Follow Up By: Mikef_patrol - Tuesday, Feb 04, 2003 at 08:38

Tuesday, Feb 04, 2003 at 08:38
Bugger

"To get L/10KM just divide " should read "To get L/100KM just divide "

MikeF
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Follow Up By: Mikef_patrol - Tuesday, Feb 04, 2003 at 08:41

Tuesday, Feb 04, 2003 at 08:41
Doh!, Must be too early in the morning

"To get L/10KM just divide 100 by your KM/L figure and voila!, L/100KM. (ie 300/35 = 8.571...=KM/L) "

Should read

To get L/100KM just divide 100 by your KM/L figure and voila!, L/100KM. (ie 100 / 8.571...= 11.67 = L/100KM)

MikeF

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Follow Up By: Savvas - Tuesday, Feb 04, 2003 at 08:46

Tuesday, Feb 04, 2003 at 08:46
Even easier way to get L/100km-

Divide your Litres by the Kilometres covered and move the decimal point 2 places to the right.
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Reply By: Savvas - Tuesday, Feb 04, 2003 at 08:42

Tuesday, Feb 04, 2003 at 08:42
I'm only guessing here.

But the only reason I can see that L/100km has been adopted as a bit of a standard over km/L, is that when the reading is higher then fuel consumption is higher. 15L/100km is higher than 10L/100km therefore there is a higher fuel usage.

If you use km/L, the higher the reading then the lower the consumption. Which must be too confusing for a standards bureaucrat.

AnswerID: 12465

Reply By: Member - Mal - Tuesday, Feb 04, 2003 at 09:50

Tuesday, Feb 04, 2003 at 09:50
The reason the government chose litres /100Km is that it expresses "consumption" whereas Km's per litre expresses a "distance" travelled for a givem amount of fuel. Thats the truth. I wonder how many public service hours it took to come to that decision?
Mal T.
AnswerID: 12468

Reply By: StephenF - Tuesday, Feb 04, 2003 at 10:00

Tuesday, Feb 04, 2003 at 10:00
We use litres/100kms because that's what the government decided when we went metric back in '74 or thereabouts. It's taken me over 25 years but I'm finally starting to wean myself off mpg and think in litres/100kms. You only have to remember that 10 litres/100kms = 28 mpg and then work proportionately, eg. 20 litres/100kms = 14 mpg, 15litres/100kms = 21 mpg.

Stephen.
AnswerID: 12470

Follow Up By: David - Tuesday, Feb 04, 2003 at 10:40

Tuesday, Feb 04, 2003 at 10:40
Well bugger me! How simple is that. This metric stuff has confused me and I still only work of mpg but at last a simple method without those fancy conversions lite take the litres divide by the Km multiply by pie r squared add the square root of the number you first thought of then add to that the cost of a pie with sauce to then realize you pressed the wrong button and have to start again.

Thanks Stephen for keeping it simple.
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Follow Up By: Old Soldier - Tuesday, Feb 04, 2003 at 11:33

Tuesday, Feb 04, 2003 at 11:33
I agree with David

Well bugger me !!

I think even my tired old "M.P.G." brain can work that out. :)

Thanks Stephen
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Follow Up By: Stephenf - Tuesday, Feb 04, 2003 at 13:27

Tuesday, Feb 04, 2003 at 13:27
Yeah, and I even managed to invent a new word - "proportionately". Before all the English teachers jump on me, I meant "proportionally".

Also, for those of you who use a spreadsheet to keep records of your fuel consumption, the formula is litres/100kms = 100*Litres used/Distance travelled.

Stephen.
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Follow Up By: Peter - Tuesday, Feb 04, 2003 at 21:49

Tuesday, Feb 04, 2003 at 21:49
stephen
not trying to be smart but i get 15ltr/1ookm and thought it was 18.8 mpg
peter
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Follow Up By: Stephenf - Wednesday, Feb 05, 2003 at 12:44

Wednesday, Feb 05, 2003 at 12:44
Peter, yes you're right. I simplified it too much. The relationship is logarithmic, not linear. While 10 litres/100kms = 28 mpg, 5=56 and 20=14, the in-between values are a bit less than proportional, eg. 15=18.8 instead of 21. Sorry about that.

Stephen.
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Reply By: ExplorOz Team - David - Tuesday, Feb 04, 2003 at 15:50

Tuesday, Feb 04, 2003 at 15:50
Hey and don't forget to migrate your spreadsheets into the Trek Fuel system. We are really trying to make this thing work and need as much data as possible. I have some excellent ideas on graphing the results and also making standard entries for vehicle types both on and off road etc etc. This is an area of the system I wish to make bigger and bigger so please help to update this stuff.

David
AnswerID: 12482

Reply By: Member - Mal - Tuesday, Feb 04, 2003 at 16:52

Tuesday, Feb 04, 2003 at 16:52
Well IAMGQ ---------- so much for "Just a quick question"!!!!!!
AnswerID: 12487

Reply By: Brian - Tuesday, Feb 04, 2003 at 18:36

Tuesday, Feb 04, 2003 at 18:36
For me the natural progression from MPG was KM/l. You think in the same mind set and the mental caculations are much easer as you work out range while driving ie no caculator.
Also if the government tells me to do it one way I am more likely to do it the other!
Brian
AnswerID: 12494

Follow Up By: Stephenf - Wednesday, Feb 05, 2003 at 13:00

Wednesday, Feb 05, 2003 at 13:00
But unless we all do it the same way we won't be able to easily compare figures. For example, km/l means nothing to me because it's a non-standard way of expressing fuel consumption. I have to divide 100 by that figure to get litres/100km, which is a standard figure I can use for comparisons.

Stephen.
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Follow Up By: Brian - Thursday, Feb 06, 2003 at 01:25

Thursday, Feb 06, 2003 at 01:25
You can say it is "non-standard" becaause it is not the offical method,
But it still does not make it the better system for calculating fuel economy (eaiser maths in km/l). Many People I talk to think that the higher the number the better you are (l/100km system) they still think the old way (mpg) but with new units (metric). I understand what you are saying "unless we all do it the same", but IMHO at the end of the day l/100 is really a usless figure ,it needs to be converted to make any use of it. Each to his own!
Brian
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Reply By: brian - Tuesday, Feb 04, 2003 at 18:47

Tuesday, Feb 04, 2003 at 18:47
it used to be miles per gallon that is distance per unit volume, this is the most usefull system of determing how far you can go on whats left in your tank at any time.knowing how far you can go on 10l or 100l is not as as efficient,seems to me this is not a way AUSSIES MEASURE FUEL CONSUMPTION,that is how far you can go on one litre, thats what we want to know. i personally am sick of the americanisation of AUSTRALIA eg we spell tyres not tires, arse is arse not ass,we have approx 4.5 l per gallon,not what the yanks have, and i reject the argument that we should have american conversion factors in fuel conversion calculations on the oz explorer site.WAKE UP AUSTRALIA WE ARE BEING OVERRUN.
be AUSTRALIAN ,BE PROUD.
AnswerID: 12497

Reply By: Dar - Friday, Feb 07, 2003 at 20:57

Friday, Feb 07, 2003 at 20:57
hi iamgq
to get mpg KM divided litres x 2.831
eg 100km divided 10 litres x 2.831 =28.31 mpg
AnswerID: 12679

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