Fuel Consumption Comparison When Buying a Car

Although we often cringe when forking out for it, fuel is a necessary expense. On average, Australians pay $78.03 per week on it, and according to the Australian Automobile Association’s Transport Affordability Index Reports it ranks as the second highest weekly car-related cost, after loan payments.

When it comes to deciding on a new car – surely a more daunting decision than choosing comprehensive car insurance! – fuel consumption comparison isn’t as straightforward as it seems. In this article we get to the bottom of the efficiency and environmental impacts of the different types of fuel, so you can choose a car that’s right for you and stretch your money further.

How to Read Fuel Consumption Labels

Figures on fuel consumption labels, which all new light vehicles in Australia are required to display, provide the number of litres a particular model of car consumes for every 100 kilometres it travels.

A laboratory that simulates different driving conditions conducts the fuel consumption comparison testing for these labels. Two test environments are studied then a combined average is calculated from there:

  1. Urban average L/100km
  2. Extra Urban average L/100km
  3. Combined Test average L/100km

The Urban figure is represents fuel consumption while driving in inner-city conditions with heavy, stop-start, local traffic.

The Extra Urban figure represents fuel consumption at slightly higher average speeds, slightly longer distances and includes trips with acceleration to reach highway speeds.

The Combined Test figure is exactly as it says – a figure that reflects a combination of both these types of driving conditions.

However, these figures are just a guide.

Even the research recognises there are big discrepancies between official test results and real-world fuel consumption. This is because testing conditions can’t possibly take into account all the different variants that affect consumption in real-world conditions.

In everyday life, aspects like traffic conditions, vehicle condition, load, engine size and even how you drive your car will affect how much fuel your car consumes. And while, say, 6L/100kms on the label is considered pretty good, it’s probably realistic to expect your actual consumption will be a bit higher.

The Lowdown on Diesel Fuel Comparison

Have you ever considered doing a diesel and petrol comparison? No? Then you might want to reconsider because diesel engines are more efficient than petrol by a whopping 30-40%. So, what’s the catch?

Yep, you guessed it. Diesel fuel costs more than petrol. You can also expect to pay a few thousand more for the privilege of owning one, but they also retain their value at time of sale.

Plus, diesel engines are more complex, meaning they have slightly higher servicing costs. Buying a secondhand diesel vehicle? It’s probably worth getting it checked by a specialist diesel mechanic before you drive away.

Another consideration is that while diesel engines emit similar C02 as petrol engines, they produce more toxic hydrocarbons, oxides of nitrogen and particulate matter. This is a bigger problem in areas with higher population density, and why a number of countries are moving to ban diesel engines.

In Australia however, the sale of diesels is still going strong and improved engine technology now includes particulate filters to reduce the unavoidable toxic emissions.

Are you a mostly urban driver? It’s important for you to know that inner city driving isn’t going to give you the cost benefits you’re looking for in a diesel engine. They reach peak efficiency while cruising at constant speeds, and suit drivers who regularly use the highway.

So, they might be better for those who regularly do longer trips, or who need the power to tow heavier loads for longer distances.

Petrol Fuel Comparison: Need to Knows

When it comes to a car fuel efficiency comparison, petrol vehicles are just plain thirsty. They use more fuel than diesel engines but it’s (only slightly) cheaper at the bowser. On the positive side, they’re quick off the mark, making them better for stop-start, inner city and suburban driving. But their consumption comes from acceleration.

Petrol engines get their power at higher revs, meaning you use the most fuel when you need to plant your foot to reach and maintain higher speeds, overtake or climb hills. This makes these cars ideal for urban driving conditions where acceleration can be managed.

The easiest way to save money on fuel in a petrol car is to take notice of how you drive. Accelerating and decelerating smoothly will help you reach your speed goals while minimising the fuel your engine guzzles.

Further, petrol has comparative C02 emissions to diesel, but don’t have the same issues with other toxic emissions due to self-regulating catalytic converters inside the cars.

Petrol cars remain the most popular choice of car in Australia, perhaps because they cost less to purchase, and maintenance and servicing costs are slightly less. Plus, they are better known so are potentially a more comfortable purchase.

LPG Fuel Consumption Comparison

While it’s on the decline, LPG (liquefied petroleum gas) is the kindest on emissions and on engines. The price for LPG is also around 50% cheaper at the pump, though that price gap is narrowing.

The catch? Cars using LPG, which is a hydrocarbon fuel comprising a mix of mostly propane and butane, consume way more fuel than any other type of car (about 20% more than petrol). So, if you buy this type of car you’ll be more intimately acquainted with your local servo. If you can find one that still has LPG.

Yep, the sale of LPG cars is on the decline. Before their closure in Australia, big manufacturers like Ford and Holden used to fit their 6 cylinder Falcons and Commodores with LPG to offset the cost of petrol in a larger 6 cylinder engine. Now there are no new cars manufactured with LPG. And while you can still convert an existing petrol engine if you have the right kind of car, you’re looking at a cost of $3000 – $5000 to do so.

What are the other benefits? LPG can potentially prolong engine life because engine oil and spark plugs need changing less often. But it’s been speculated that cheaper servicing costs might climb as the cars get rarer.

And if you’re a fairly keen road-tripper, they’re probably not the car for you. A combination of their fuel-guzzling nature, and the increasing rarity of LPG will mean you need to plan your trip well to ensure you don’t run dry. We’re guessing this might turn most people off.

How to Choose a Car that Makes Your Fuel Money Go Further

To make the most appropriate choice about fuel consumption for you, use the comparison label as a guide. Also carefully consider your budget, lifestyle, circumstances and driving style. In combination with the info above, these questions might help you decide…

What kind of driver are you?

  1. A take-your-time-but-leave-early-driver, who is chill behind the wheel
  2. A competitive and impatient lead-foot (with a bad tailgating habit)
  3. Relaxed, but like to get up to speed quickly

What type of driving do you do most?

  1. Short trips that are mostly local, inner city and suburban driving
  2. Suburban driving, with an average of 15 – 30 mins in a car
  3. Regular highway driving (about an hour each week) but usually not far
  4. Lots of long or interstate travelling, on highways and some local

Over to You – Any Fuel Consumption Comparison Insights?

How much do you spend on fuel each week? Have you bought/considered buying something other than a petrol car before? We’d love to know – comment below or head to this story on our Facebook page.

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