Best ways to measure fuel economy??

Submitted: Thursday, Jan 24, 2008 at 10:10
ThreadID: 53849 Views:3909 Replies:9 FollowUps:2
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Howdy troops...

Just a quick one. Can I ask what way you measure your fuel economy? Whats the most accurate way?

Cheers in advance...

Ro
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Reply By: Wizard1 - Thursday, Jan 24, 2008 at 10:52

Thursday, Jan 24, 2008 at 10:52
Fuel economy calculation 101

1. Fill car with fuel
2. Drive car.
3. Re-fuel and record how far you travelled on the last load of fuel
4. Divide litres used by km travelled and multiply by 100

eg. You travel 500 km and use 50 litres (not in a 70 series though LOL).

50/500 x 100 = 10L/100 km

I don't use the km/litre as it isn't the accepted and most used economy method.

No brainer really. If you want anthing more accurate it needs to be done in a lab, etc.

AnswerID: 283483

Reply By: Member - Big Al. Gold Coast - Thursday, Jan 24, 2008 at 11:05

Thursday, Jan 24, 2008 at 11:05
Don't rely on the trip meter, use the speed odometer or better still use the known distance between too towns .
AnswerID: 283485

Reply By: Notso - Thursday, Jan 24, 2008 at 11:06

Thursday, Jan 24, 2008 at 11:06
As above but make sure you fill your tank on the same sort of angle as the original fill and also try to do it over a number of trips, Make notes about the conditions, eg headwinds, tail winds up and down hilss etc. Then you'll get a fair average as well as an idea of what you get travelling into a head wind, up and down hills etc
AnswerID: 283486

Reply By: pjd - Thursday, Jan 24, 2008 at 11:12

Thursday, Jan 24, 2008 at 11:12
try this web site its very easy
http://www.dropbears.com/u/utilities/fuel_efficiency.html
AnswerID: 283488

Reply By: Gerhardp1 - Thursday, Jan 24, 2008 at 11:48

Thursday, Jan 24, 2008 at 11:48
These days, it's one of those things that you don't want to know.

Same applies for how many litres of water women flush down the toilet every day, and how much of your money governments waste.
AnswerID: 283491

Reply By: Member - Bucky (VIC) - Thursday, Jan 24, 2008 at 15:46

Thursday, Jan 24, 2008 at 15:46
the best way to measure fuel economy is to continuously monitor it, ie used fuel vs km's driven, in all conditions.

Doing it once or twice will mean nothing, unless you are doing a long run.

For example ,, I consistently get 9.5 km/lt from our Navara, all local work.
Chuck in a trip up the Hume Freeway to Albury @ 112 km/h and I get 10.5km/lt ( why, ? probably spinning motor easier, suited to vehicle )

Tow our camper, I get 7-8 km/lt, and chuck in a run up into the desert, fully loaded, towing camper, I get 6.5 km/lt

Its all about keeping good records. Simple as that !
Cheers Bucky
AnswerID: 283527

Reply By: Member - Olcoolone (S.A) - Thursday, Jan 24, 2008 at 17:52

Thursday, Jan 24, 2008 at 17:52
Why do people use kilometers per litre, litres per 100k gives you a better undersatnding and is easier to workout.

Regards Richard
AnswerID: 283566

Follow Up By: Member - Alan H (Narangba QLD - Thursday, Jan 24, 2008 at 18:15

Thursday, Jan 24, 2008 at 18:15
I believe it is about concepts. Some do not like the 100km bit yet the degree of accuracy is much greater to use l/100km.

EG What if I drive 1530km and use 100litres of fuel

This is 15.3 km/litre or 6.5 l/100km(one decimal place)

The real concept to be grasped is what difference does a decimal point really make in the real world.

If the 15.3km/litre went to 15.4km/l you travel an extra 10km on the same 100l of fuel

If the 6.5/100km went to 6.4l/100km it means you travel another 30km on the same 100km fuel.

Does it really matter? I don't think so it just matter whether you like better consumption to be a bigger number (km/l) or whether you like better consumption to be a smaller number (l/100km)

As stated, an average consumption the whole use of the vehicle is probably more real as life is about variety and each trip will be different and have different fuel consumption.
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FollowupID: 548191

Follow Up By: Member - Poppy (QLD) - Thursday, Jan 24, 2008 at 18:23

Thursday, Jan 24, 2008 at 18:23
Some of us come from the old days of gallons per mile, so I reckon it was an easier adjustment
My old Charger used to get 28 mile/ gallon and I don't even want to think how much fuel was then.
Tyres used to be the biggest expense in running a car in those days
Cheers Ray
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FollowupID: 548196

Reply By: disco driver - Thursday, Jan 24, 2008 at 19:14

Thursday, Jan 24, 2008 at 19:14
Hi Ro,
Short of using sophisticated and therefor expensive flowmeters and distance recording (fifth wheel) gear the easiest way is to fill the tank right up, reset the trip meter and record all fuel used over a reasonable period of time and the total distance travelled. Go back to the same servo and refill the tank right up again.
Then it's just a matter of doing the maths as above.

IMHO once you know what your vehicle does in terms of average fuel economy under most conditions (head/tail winds, fully loaded/empty, towing/not towing) it's not important any more.

Even with the price of diesel at $1.559/litre here, I don't bother worrying about fuel consumption. If I want to go somewhere, I go.
Life is too short for me to worry about the difference between diesel @ $1.35 and $1.559/Litre, or fuel use at 10L/100km and14L/100km when planning a trip.

Just my opinion, whether you agree with me or not is of no consequence to me

Disco.
AnswerID: 283586

Reply By: Mike Harding - Thursday, Jan 24, 2008 at 19:24

Thursday, Jan 24, 2008 at 19:24
>Whats the most accurate way?

See my reply to Steve-wots-is-name.

Basically... there isn't one - a dynamometer is a pretty good guide because it's consistent but it cannot calculate wind resistance or traffic (read driver) issues .

For most of us the best way is to average your fuel usage over (say) 50 tanks of fuel.

Mike Harding
AnswerID: 283588

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