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