Coaching Centre
Running a car
Fuel consumption in litres per 100 km, fuel costs for trips and for a year, electric car charging costs, yearly running costs, and cost per week and per kilometre.
Once a car is yours, it keeps costing money: fuel, servicing, tyres, rego and insurance every year. The NRMA estimates that running a small car costs well over $\$100$ a week once everything is counted. This section is about adding that up honestly.
Fuel consumption
In Australia, fuel consumption is given in litres per 100 kilometres (L/100 km). A car rated at $7.5$ L/100 km burns $7.5$ litres of fuel for every $100$ km it travels. Lower is better.
Ella fills her tank, drives $560$ km, then needs $42$ L to fill it again. Find her car's fuel consumption.
The same car drives $12\,000$ km a year and petrol costs $\$2.05$ a litre. Find the yearly fuel cost.
Electric cars
An electric car's energy use is given in kilowatt-hours per 100 km. A typical small EV uses about $16$ kWh/100 km. Charged at home on a household rate of $35$ cents per kWh, the same $12\,000$ km uses $120 \times 16 = 1920$ kWh, costing $1920 \times 0.35 = \$672$. Charging during the day from rooftop solar, or on a cheap overnight tariff, costs even less, while fast chargers on the highway cost more.
Check Example 2 and the electric car figure above. How high would the electricity price need to be before charging costs as much as petrol?
Set $20\,000$ km a year. How much does the electric car save each week? An EV costs about $\$12{,}000$ more to buy. Roughly how many years would the savings take to cover that?
The full yearly cost
A car's yearly costs are: rego $\$450$, green slip $\$600$, comprehensive insurance $\$1100$, servicing $\$500$, tyres $\$250$ and fuel $\$1800$. It drives $12\,000$ km a year. Find the cost per week and per kilometre.
Your turn
Car A uses $6.5$ L/100 km and car B uses $9.0$ L/100 km. Each drives $15\,000$ km a year with petrol at $\$2.00$ a litre. How much more does car B spend on fuel each year?
Show the working
The difference is $2.5$ L per 100 km. Over $150$ lots of 100 km: $150 \times 2.5 = 375$ L. At $\$2.00$ a litre, that's $\$750$ a year.
A car uses $36$ L to travel $480$ km. Find its fuel consumption in L/100 km.
$36 \div 480 \times 100 = 7.5$ L/100 km.
A car uses $8.2$ L/100 km. How much fuel does it need for a $350$ km trip?
$350 \div 100 = 3.5$ lots. $3.5 \times 8.2 = 28.7$ L.
Petrol costs $\$1.98$ a litre. Find the cost of $28.7$ L, to the nearest cent.
$28.7 \times 1.98 = \$56.826$, which is $\$56.83$.
An electric car uses $15$ kWh/100 km. Find the cost of charging for a $200$ km drive at $30$ cents per kWh.
Energy: $2 \times 15 = 30$ kWh. Cost: $30 \times 0.30 = \$9$.
A car's yearly costs total $\$4700$. Find the cost per week.
$4700 \div 52 \approx \$90.38$.
A car rated at $6$ L/100 km:
L/100 km means litres used per 100 kilometres travelled.
A car costs $\$4700$ a year to run and drives $12\,000$ km. Find the cost per km, to the nearest cent.
$4700 \div 12\,000 \approx \$0.39$, so $39$ cents per km.
A car with a $50$ L tank uses $6.25$ L/100 km. How far can it travel on a full tank?
$50 \div 6.25 = 8$ lots of 100 km, so $800$ km.
Exam style: Jake drives $250$ km a week in a car that uses $7.2$ L/100 km. Petrol costs $\$2.10$ a litre. Find his weekly fuel cost.
Fuel: $2.5 \times 7.2 = 18$ L. Cost: $18 \times 2.10 = \$37.80$.
Exam style: A petrol car uses $7.5$ L/100 km with fuel at $\$2.05$ a litre. An electric car uses $16$ kWh/100 km with power at $35$ cents per kWh. Each drives $12\,000$ km a year. How much does the electric car save on fuel per year?
Petrol: $120 \times 7.5 \times 2.05 = \$1845$. Electric: $120 \times 16 \times 0.35 = \$672$. Saving: $1845 - 672 = \$1173$.