Perform calculations regarding fuel consumption and prices

THERE’S MORE TO A CAR THAN THE PRICE TAG...

So our car is purchased, registered and insured. A considerable amount of money goes into the purchase of a car, but there’s even more to it. We’ve gotten the car onto the road, now we have to keep it there.

Running Costs

To keep a car useable and roadworthy, there are ongoing costs that will last throughout the life of the car.

The most obvious is fuel.

However, we need to be aware of costs involved in servicing the car, any repairs, tire wear, parking, tolls etc. and on top of these; the standing costs of paying off a loan on the car (and interest), registration, insurance and the fact that the car’s value depreciates!

Having already looked at insurance, the next biggest cost is the life blood of your engine.

When it comes to fuel and cars, we have two questions.

• How much fuel does my car use?

• How much does fuel cost?

If we can answer these, we’ll be able to make better decisions on how much money we’re going to spend to keep the car in use.

Fuel Consumption

When we talk about how much fuel a car uses, we measure it as a rate.

Just like speed is measured in km/h or m/s, fuel consumption is usually measured in

Litres Per Kilometre ( L / km )

or 

Litres Per 100 Kilometres ( L / 100 km ) 

We can use any volume measure (Litres, metres³, millilitres etc.) against a distance measure (kilometres, metres, centimetres).

But in most cases we stick to larger quantities like Litres and 100’s of kilometres simply because of the inaccuracies involved in measuring fuel consumption. Let’s discuss this point:

You may have seen a fuel consumption sticker, like the one below, on cars these days. They give drivers a good indication of a car's fuel consumption as an average (combined), in city driving (urban) and highway driving (extra urban) as well as carbon dioxide emissions.Whilst this gives a reasonable figure on the fuel consumption, car manufacturers get these values under IDEAL lab conditions. So going back to inaccuracies, fuel consumption can vary depending on:

• Road conditions,
• Traffic,
• Weather,
• Car Speed,
• Car Weight, and
• Driving style.

Using L/100km helps create an average figure that will smooth out slight variations in fuel consumption. We can measure average fuel consumption ourselves. By knowing how much fuel is in the tank and how far we travelled, we can get a rate in Litres per "however many kilometres we drove".

Example

Jake pumps $30$30 L of fuel into his car and resets his trip odometer. By measuring how far he travelled on that 30L he can come to a good approximation of his average fuel consumption.

So if Jake managed to travel $300$300 km on $30$30 L, we can represent his fuel consumption as follows:

$30$30 L / $300$300 km	$=$=	$10$10 L / $100$100 km

These rates, whilst being an average, can give you a bit of an image as to who much fuel your car uses. Having an idea of fuel consumption can help you figure out how much fuel you might need for a certain distance…or how far you can travel on $20 worth of fuel!

Now, let’s take a look at a few different cars and compare their quoted fuel consumption.

Note: All these vehicles have V6 engines and are of comparable size.

Compare cars of your choice here: http://www.greenvehicleguide.gov.au/GVGPublicUI/Home.aspx

And for older cars: http://www.environment.gov.au/settlements/transport/fuelguide/search.html

You can use a number of online fuel consumption calculators to assist you, such as this one:

http://motormouth.com.au/myvehicle/consumptioncalculator.aspx

 

Worked Examples

Question 1

Question 2

Question 3