Fuel calcs

[tkn]

Decided to put this here because Ute/Tray Back section seems "unknown" - but it applies to all vehicles.

Fuel prices will get to $1.50 per litre (for real fuel, probably $0.85 for gas) pretty soon.
What follows might help you to reduce your fuel bills -
Say your vehicle is using 14L of fuel per 100km and usually its on road weight is 2400Kg (with all the stuff you carry around in it).
That translates as about 6 millilitres of fuel for each 1Kg that travels 100km
i.e. 14000 millilitres of fuel / 2400Kg = 5.83333 millilitres/Kg

Lets say an auxiliary battery weighs 20Kg, then to carry that battery 100km would use –
20 x 5.8333 = 116.67 millilitres of fuel.
If you travel 1000km with the battery, then it would be 10 x 116.67 = 1.167 Litres/1000km
If you average say 40000km per year, then 40 x 1.167 = 46.68 Litres p.a. to cart the battery around.
Which at current prices works out to be 46.68 x $1.30 = $60.68 p.a.
That might not seem like a lot, but if you carry 2 auxiliary batteries then it is costing you about $121 p.a. for the privilege.

This makes the calculation simpler –
U = Fuel usage per 100km (Litres)/GVM x Weight of Items x 1% of Distance travelled p.a.
e.g. using the 2 x battery figures above is 14/2400 x 40 x 40000/100 = 93.33
and Cost = U x fuel price per litre
e.g. 93.33 x $1.30 = $121.33

Now, in the real world, you can add up the weight of all the half Tonne of “extra stuff” in your vehicle and divide it into essentials like tools, winch, compressor, extra wheel, shackles, ropes, etc. AND all the other crap that somehow finds its way into your vehicle, then calculate what it is costing you each year to carry it around.
e.g. Essentials - 14/2400 x 200 x 40000/100 = 466.67 and 466.67 x $1.30 = $606.67 p.a.
Crap - 14/2400 x 300 x 40000/100 = 700 and 700 x $1.30 = $910 p.a.

If you are planning a trip of say 15000km with 600Kg of gear and where fuel stops are going to be few and far between, then reduce your fuel economy from say 14L/100km to 18L/100km (because you’re going to be fully loaded) and use the calculator to decide what to leave at home.
e.g. 18/3000 x 600 x 15000/100 = 540
AND 540 x $1.30 = $702.00 (which represents the additional cost of travelling with 600Kg of extra camping gear, food, clothes, etc.)

This does not include additional wear and tear on the vehicle and additional servicing costs – if you want to estimate that, then add 150%
e.g. $702 + $1053 = $1755.00 for your 15000km trip
If the roads are really rough, plenty of dust and mud, etc. double that figure e.g. $3500.00

[Bob]

You have just ruined my day. Knew fuel costs were high but i liked to put my head in the sand.

Having said that thankyou for your post which does put it all in perspective

[tkn]

You have just ruined my day

Sorry, Bob.

[Bigrig]

Top post mate, but you just killed everyone's plans of ever travelling again!!! LOL ...

Nice easy way to calculate the cost, only problem I can see is knowing the weight of said "crap". I know the weight of the truck, but wouldn't have the first clue about the weight once ladened with camping gear etc.

[MQ MAD]

14l/100Ks outta the TB42e

Where,where
Is there an economical version ???
(they average 20-25L/100Ks)

I look at it like this
IF ya want to drive a 3 tonne 4x4 (extra with add ons) with the aerodynamics of a block of flats
Economy isnt in the equation

I could run an XY GT 351 , with a tuff as nails 351 , that would get the same if not similar economy as my GQ
Now only to get the XY falc to do what the GQ can !!!

[the evil twin]

Uuummm I hate to be a wet blanket but there is a flaw in your logic.

I must say that I totally agree that removing weight WILL save fuel but the "weight" to "fuel used" ratio isn't a direct percentage like your equation as weight doesn't determine your fuel useage to a very great degree compared to other factors.

The variable amount of fuel required (as opposed the the set amount against drive losses etc) is determined predominantly by rolling friction and drag. The weight of the vehicle and its contents has no effect on drag so adding removing anything doesn't matter. Rolling friction is affected but the effect can be reduced but not nullified by appropriate tyre pressures.

Hypothetically, an example to illustrate. Two identical vehicles with a tare of 2200 KG do an identical trip of lets say 1000 K's. One has the Driver only so a GVM of 2300 (2200 plus 100) and lets say the other has Driver and 3 Pax and 400 Kg of gear so a GVM of 2200 plus 400 plus 400 which is 3000 or roughly 1/3rd more. Now I deliberately choose those figures because they are what we do a fair bit at work.

The heavier vehicle won't use anything like 30% more fuel indeed in a CRD the fuel useage would change by less than 1 litre per 100K's so it would use about 7% more at the max but willing to concede 10% (No way in real life I might add) for the sake of discussion but nothing like 30%.

In my Patrol (or the work vehicles) I would actually save more fuel if I took my roof rack off as drag is exponential so whilst I reduce weight as well the big saving is in reduced drag.

Again, I agree that taking weight out saves fuel, just saying the magnitude of the saving is much less than the formula so you might need to add another divisor of say 5 as a guesstimate as the $910 would be closer to $200 maybe $250.

We usually do Perth Carnarvon with Driver changes at 1/2 way Mill, Gerro and Billabong. The difference in fuel used between "two up and light on" and a "full vehicle around the GVM" when we gas up at Carnarvon at the end of the day is about 10 to 15 litres

[Bigrig]

Uuummm I hate to be a wet blanket but there is a flaw in your logic.

I must say that I totally agree that removing weight WILL save fuel but the "weight" to "fuel used" ratio isn't a direct percentage like your equation as weight doesn't determine your fuel useage to a very great degree compared to other factors.

The variable amount of fuel required (as opposed the the set amount against drive losses etc) is determined predominantly by rolling friction and drag. The weight of the vehicle and its contents has no effect on drag so adding removing anything doesn't matter. Rolling friction is affected but the effect can be reduced but not nullified by appropriate tyre pressures.

Hypothetically, an example to illustrate. Two identical vehicles with a tare of 2200 KG do an identical trip of lets say 1000 K's. One has the Driver only so a GVM of 2300 (2200 plus 100) and lets say the other has Driver and 3 Pax and 400 Kg of gear so a GVM of 2200 plus 400 plus 400 which is 3000 or roughly 1/3rd more. Now I deliberately choose those figures because they are what we do a fair bit at work.

The heavier vehicle won't use anything like 30% more fuel indeed in a CRD the fuel useage would change by less than 1 litre per 100K's so it would use about 7% more at the max but willing to concede 10% (No way in real life I might add) for the sake of discussion but nothing like 30%.

In my Patrol (or the work vehicles) I would actually save more fuel if I took my roof rack off as drag is exponential so whilst I reduce weight as well the big saving is in reduced drag.

Again, I agree that taking weight out saves fuel, just saying the magnitude of the saving is much less than the formula so you might need to add another divisor of say 5 as a guesstimate as the $910 would be closer to $200 maybe $250.

We usually do Perth Carnarvon with Driver changes at 1/2 way Mill, Gerro and Billabong. The difference in fuel used between "two up and light on" and a "full vehicle around the GVM" when we gas up at Carnarvon at the end of the day is about 10 to 15 litres

So extra weight equals extra fuel generally speaking ... will that do? Usually the metric I use!!! LOL Weight also equals greater revs to create greater power for potentially a greater time when stop/starting also, and that goes a long way towards affecting consumption also. Great posts from all though .... Good topic!

[MQ MAD]

Whats economy IF ya need the power for pulling the wieght ???
Compare a GU 2.8 Vs a GQ 4.2 pettie
I use these as i had a GU,now the GQ
Pulling loads up hills the TB does it with absolute ease,wheres as the same for the GU its a bit harder
You have to flog the smaller engine harder to do what the larger engine does
This then results in the smaller engine using more fuel
Then there is the aerodynamics to factor
But,is this that relevant
Comparison ,
A new camry returns 9-10l/100Ks economy,
Sleek late model car
But My old MQ 3 tonne brick returned the same economy

Excess wieght does effect economy some what
But next trip ya do just mention to the minister she must stay home,cause ya wanna save a few $$$ on fuel
I think sleepin on the couch wont be nice

[Bigrig]

Whats economy IF ya need the power for pulling the wieght ???
Compare a GU 2.8 Vs a GQ 4.2 pettie
I use these as i had a GU,now the GQ
Pulling loads up hills the TB does it with absolute ease,wheres as the same for the GU its a bit harder
You have to flog the smaller engine harder to do what the larger engine does
This then results in the smaller engine using more fuel
Then there is the aerodynamics to factor
But,is this that relevant
Comparison ,
A new camry returns 9-10l/100Ks economy,
Sleek late model car
But My old MQ 3 tonne brick returned the same economy

Excess wieght does effect economy some what
But next trip ya do just mention to the minister she must stay home,cause ya wanna save a few $$$ on fuel
I think sleepin on the couch wont be nice

LOL!! point taken .. and btw, she won't travel in Tank anyway - goes everywhere in the rubicon!!! So I'm on a winner there!!

Engine technology has a lot to do with it, as does aerodynamics, weight, gearing, tyre pressure, road type, etc ... the way I figure it, you buy what you know you can afford to run ... and in working that out, add 50% to what you think you are going to pay - reason? You'll probably do more off road which is nearly impossible to predict, and fuel prices aren't going to go down OR stay static over the life of the vehicle ... they'll only rise unfortunately!

[nowoolies]

hay mad
you come around and tell her who must be obeyed
im going down the pub,................ give me a call and let me know what emergency ward your in ill come a say g`day
rotflmao

[nowoolies]

on the subject of fuel my local Nissan service centre were horrified at my fuel usage average 5.48 klm per litre on road, off road ,o/drive on , o/drive off , fully loaded, and totally empty, all tests i have done are on the 100klm mark as requested by Nissan
and they as i have had, a bitch at Nissan Australia.
now Nissan Australia want to do their version of the above on Monday
ill post their results as they come in

[Maxhead]

on the subject of fuel my local Nissan service centre were horrified at my fuel usage average 5.48 klm per litre on road, off road ,o/drive on , o/drive off , fully loaded, and totally empty, all tests i have done are on the 100klm mark as requested by Nissan
and they as i have had, a bitch at Nissan Australia.
now Nissan Australia want to do their version of the above on Monday
ill post their results as they come in

It will be interesting to see what they have to say...not a lot I reckon or " Please accept"....

[MQ MAD]

To give some an idea of fuel consumption
A GTHO Phase 3 Falcon on full song gets 2.5Ks/L
Thats according to a magazine report done in the 70s when they were tested new

Dont get me wrong,i like my fourbies,but sheeet if ya gunna get that economy from really a 3 tonne slug
Im gunna go buy a tuff asss V8

Woolies,
Sorry there bud,cant help with your minister problem
Ive got enuf trouble on the war front here

[tkn]

For the fuel figures I used what I am getting out of a GQ diesel cab chassis that weighs about 2400Kg on the road most of the time. 14L/100km is about right, up (or down) to about 16L/100km uphill and/or into a headwind.

Be good to know what other diesels are getting.
TB42 are notorious for woeful fuel economy, but even so figures seem to vary between 30L/100km and 20L/100Km.

How about some posts giving details of petrol or diesel, engine size, year and usual fuel economy.

[MQ MAD]

Not sure IF ive posted this before,
But
MQ SD33 n/a (non turbo) 4 speed wagon 10L/100Ks
Thats on a highway trip with no trailer
TB42 GQs are around the 20-25L/100Ks
But the difference between the TB42 and the TD42 , we dont need turbos to get jiggy with it
They make quite amble power from factory

[tkn]

But the difference between the TB42 and the TD42 , we dont need turbos to get jiggy with it
They make quite amble power from factory

Yeah, got to agree they do "amble" behind turbos. Must be they spend a lot of time drinking - or should that be "guzzling!" - petrol or butane or other non-diesel substances.

For us turbo freaks, an aid to better economy can be the boost gauge. Like driving within the range of 1 to 5 psi - except for major hills and overtaking.

A slight lift off the accelerator often does not mean any change in speed - but does mean less fuel usage.

I know there will be those who say "You can't get something for nothing." but try it - you might be surprised.

[the evil twin]

Not sure IF ive posted this before,
But
MQ SD33 n/a (non turbo) 4 speed wagon 10L/100Ks
Thats on a highway trip with no trailer
TB42 GQs are around the 20-25L/100Ks
But the difference between the TB42 and the TD42 , we dont need turbos to get jiggy with it
They make quite amble power from factory

Yeah... over about 80,000 K's my TB42 used to return 18 to 19 LPH which went up to about 22 after the lift, larger tyres, roofrack etc

Used to fall asleep waiting for the N/A TD42's to catch up... the Turbo's could at least get to where the Petty's were waiting before you finished the first beer

[hekarewe]

instead of just sitting down with our calculators and seeeing what we can strip out then cal what we havwe saved wouldnt make more sence to have a thread where if we see cheap fuel we list the location and day and time we saw it andhow much it was.

which comes to my next thing is there a web site that we can go to too try and see how much fuel will be in places like cape york while i am up there in june july???

[the evil twin]

WA has this... http://www.fuelwatch.wa.gov.au/fuelwatch/pages/home.jspx

As for trying to predict the price of juice up the Cape 3 months ahead... tad difficult methinks

[hekarewe]

no harm in being an optimist LOL :)

[MQ MAD]

Its quite funny IF we posted cheap servo prices
How many brain farts do we here about that will drive from 1 side of town to the other
Just to save 1c a litre, then only buy like $10 worth
Theres a local ol bloke (craft disease ???)
He will drive a 50K round trip to save 50c on a tin of cat food
Oh and only buy 2 or 3 tins

[hekarewe]

Its quite funny IF we posted cheap servo prices
How many brain farts do we here about that will drive from 1 side of town to the other
Just to save 1c a litre, then only buy like $10 worth
Theres a local ol bloke (craft disease ???)
He will drive a 50K round trip to save 50c on a tin of cat food
Oh and only buy 2 or 3 tins

that just pure gold but sadly true just about wet myself reading this. all i can say to this is there is no cure for stupid, but is there was such a page/thread then one only (chock gigggle) that common (smirk) sense would prevail ROFLMAO no i am being serieous honest LOL

[Bigrig]

Tank returned 20.79 litres per hundred on gas on the return trip from Sydney yesterday. That's with me, luggage for four, some camping gear, the eldest son (weighs about 70kg), and the air con running for about a third of the trip - absolutely stoked!!! Problem is, averaged 74.9 cents per litre for it ... LPG is moving up at a far higher rate than petrol and diesel for some reason ...

[the evil twin]

Tank returned 20.79 litres per hundred on gas on the return trip from Sydney yesterday. That's with me, luggage for four, some camping gear, the eldest son (weighs about 70kg), and the air con running for about a third of the trip - absolutely stoked!!! Problem is, averaged 74.9 cents per litre for it ... LPG is moving up at a far higher rate than petrol and diesel for some reason ...

20 LPH on gas is very very good... Kudo's for that.

The price is going up faster in relativity because the Gov't is reducing the subsidy. The LPG susbsidy will be completely gone by 2015. It was supposed to be gone by 2012 originally but they kept it going a little longer.

[boggy2006]

85c/l for gas, sheesh, why is that going up 30% and petrol only like 5%?

Anyway, good calcs, but fuel consumption is not just dependent on weight so the saving won't be proportional to the weight reduction. What we need to do is lower the Patrols, give them a pointy front end, small diesel engine ..... and halve the weight!!

[Bigrig]

85c/l for gas, sheesh, why is that going up 30% and petrol only like 5%?

Anyway, good calcs, but fuel consumption is not just dependent on weight so the saving won't be proportional to the weight reduction. What we need to do is lower the Patrols, give them a pointy front end, small diesel engine ..... and halve the weight!!

What? Are you suggesting my besser block on wheels is not aerodynamic?? LOL ...

[boggy2006]

What? Are you suggesting my besser block on wheels is not aerodynamic?? LOL ...

unless a bus is! LOL

[MQ MAD]

LPG is goin up !!!!!

So the government has been paying $1500 towards the conversion because they are nice kind hearted people ???
Or
Its a polite way of lubing that thing they will drive up ya bum ???

[Bigrig]

LPG is goin up !!!!!

So the government has been paying $1500 towards the conversion because they are nice kind hearted people ???
Or
Its a polite way of lubing that thing they will drive up ya bum ???

Ooo ... Oooo ... pick me ... pick me ... I know the answer!!!!! LOL ...

[tkn]

Top post mate, but you just killed everyone's plans of ever travelling again!!! LOL ...

Nice easy way to calculate the cost, only problem I can see is knowing the weight of said "crap". I know the weight of the truck, but wouldn't have the first clue about the weight once ladened with camping gear etc.

Grab a bathroom scale - they will usually weigh items up to about 140Kg - then weigh all the bits and pieces, toolboxes, air compressor, generator, tent(s), tarps, etc., etc.

Some things have fixed weights (give or take a kilo) -

Spare wheel = 35Kg
Jerry can of water (20 litres) = 20Kg
Jerry can of fuel (20 litres) = 19Kg
Car battery = 15Kg
"truck" battery = 20Kg
Small generator = 25Kg
2 man polyester tent = 5Kg
Family polyester tent = 60Kg including fly and poles

Add it all up - then add it up again because you will think you have made a mistake.
Then decide what you can put in the shed.

You can do the same thing when loading a camper trailer or caravan -
(a) to help prevent overloading
(b) to help balance the load front to back and side to side

If the ball weight of your camper or caravan is around 100Kg, use the bathroom scale to check that it is within 10Kg of what it should be.

[MQ MAD]

Yep good point
Sure adds up
Now im lost on the leaving all the gear and the family behind
It will work
Trading 200Kg of grog , sleeping in the car
Wont it ???

Think the saving would save on the headache
Thats for sure
Nag nag nag nag
PS
Gotta be nice the minister is between here and the fridge
Wish me luck

[hekarewe]

Grab a bathroom scale - they will usually weigh items up to about 140Kg - then weigh all the bits and pieces, toolboxes, air compressor, generator, tent(s), tarps, etc., etc.

Some things have fixed weights (give or take a kilo) -

Spare wheel = 35Kg
Jerry can of water (20 litres) = 20Kg
Jerry can of fuel (20 litres) = 19Kg
Car battery = 15Kg
"truck" battery = 20Kg
Small generator = 25Kg
2 man polyester tent = 5Kg
Family polyester tent = 60Kg including fly and poles

Add it all up - then add it up again because you will think you have made a mistake.
Then decide what you can put in the shed.

You can do the same thing when loading a camper trailer or caravan -
(a) to help prevent overloading
(b) to help balance the load front to back and side to side

If the ball weight of your camper or caravan is around 100Kg, use the bathroom scale to check that it is within 10Kg of what it should be.

christ by the time i did all that my holidays would be over!!!!

"so what did you do for your time of?"

"had a ball measured and wieght all my camping gear so i would know how much fuel i would use so much fun i was beside myself"

"poor bastard needs a life"

i know this comment will come back and bite me lol

[Bigrig]

christ by the time i did all that my holidays would be over!!!!

"so what did you do for your time of?"

"had a ball measured and wieght all my camping gear so i would know how much fuel i would use so much fun i was beside myself"

"poor bastard needs a life"

i know this comment will come back and bite me lol

I've already spoken to the blokes at the local tip - a tenner in their pocket and they'll weigh the rig before we leave - if it's over the limit, trips off!!! LMFAO!!!

[hekarewe]

that will work but will be a short trip for me 2 girls on board need i say more

[Bigrig]

I hear ya mate - I've got two of them also, and a missus to make it three .... oh ... And two boys that probably count also!!! LOL

[MQ MAD]

All the family in the trailer,with quick release couplin
When they give ya the sh*ts,just release the trailer
Youll have a wonderfull holiday
But looking for a new place to live when ya get home could pose an issue

[damianovdd]

If i go logicaly, then when we past 2wd to 4wd we must multiply by 2 the fuel consumption. So if 2wd make 10/100, then 4wd must do 20/100... Is the calculation goes that way?

[tkn]

If i go logicaly, then when we past 2wd to 4wd we must multiply by 2 the fuel consumption. So if 2wd make 10/100, then 4wd must do 20/100... Is the calculation goes that way?

Yeah, thats about it.

Especially in sand, fuel usage goes from say 7km/litre down to as little as 3km/litre. Desert holidays can get real expensive.

[Simon]

Are you an accountant TKN?

[MQ MAD]

Seems he is just a dedicated bloke trying to save money on our juice guzzlers
If he was an accountant , he would trying to tear money from us

Thats the polite way to describe an accountant on a public forum

[tkn]

Not an accountant nor a lawyer neither.

But not against saving a couple of thousand dollars a year
e.g. 60000km @ 6km/litre = 10,000 litres of fuel used and 60000 @ 7km/litre = 8571 litres of fuel used - 10000 - 8571 = 1429 : 1429 litres x $1.50 = $2143.50 savings on fuel cost p.a.

Worth having in my pocket I reckon.

[cnw351]

Great info, thank you. I do believe fuel is going to keep rising and that we will surpass the 2006 highs. But hey, the couch does get comfy, so the trips can still happen.

[speedway]

I don't worry about the cost of fuel just how far I can go on what I carry. For my trip to Lake Eyre after easter I will load up 2 205lt drums and 4 20lt cans onto the back of the ute and head off, that should give me about 4000K's, the fuel will cost me about $225.00 as I make my own (Bio-diesel) about 40c per lt, so the weight dosent worry me either as I have somewhere to offload it as a base and the tank + 4X20lt drums give me about 1000K's.
Is there anyone else using Bio-diesel in their patrol out there?
Keith.