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Diesel vs Petrol: A car-buying guide

Wondering whether you'll save in the long run with a diesel purchase? Here's what you need to know to make a decision.


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Diesel cars have come a long way in recent years. While petrol may have been obvious ten years ago, the introduction of luxury diesel alternatives and improvements in technology have closed the gap. Want to make the right decision for your next car purchase? The guide below outlines all the variables to factor into your decision.

How much will you save?

The main reason people opt for diesel cars is to save money on fuel. However, because diesel cars are usually a few thousand dollars (10-15%) more expensive than their petrol-alternatives, you need to factor that into your purchase decision. Some car companies claim that diesel vehicles use around 30% less fuel than petrol vehicles. This figure will vary depending on the size of the vehicle and how you drive it and in some cases may be closer to the 15-20% mark.

According to a study by the NRMA Motoring & Services, which compared four vehicles with petrol and diesel variants, the vehicles with diesel used 20% less fuel on average. The highest reduction in fuel consumption was from the Holden Epica by 33%. The lowest was the Hyundai Sonata, which saw a fuel consumption reduction of 13%.

Data Source: ABS

What about performance?

Petrol cars are generally more powerful than diesel. However, power isn't everything. Diesel vehicles can deliver a large amount of torque at low revs, so if you're travelling at 1,500 - 2,500rpm you'll power ahead. This makes diesel better for cruising, whereas petrol cars are better for speed.

Higher servicing costs of diesel cars

Diesel vehicles come with notoriously higher costs for servicing and upkeep. These vehicles need diesel-specific oils, filters and coolants that can come with a higher price-tag. According to an RACQ factsheet, a Hyundai i30 Active petrol costs 5.95c per kilometre in services and repairs, while the diesel costs 6.37c per kilometre. If you look at your fuel savings on that same vehicle, the petrol version will cost you 9.49c per km and you'll pay 6.78c per km for diesel. That's a fuel saving of 28.55%.

If you don't maintain a diesel vehicle you can run into a lot of problems, especially with the engine. Diesel cars are much better for drivers of long distances. A diesel engine, if it conforms to the Euro 5 emission standard, will have a filter built-in, and it's only when the car is driven a certain distance will the filter perform effectively. If it doesn't, you'll be feeling the regret with a sizeable mechanic's bill.

Compare a range of car loan options

Data indicated here is updated regularly
Name Product Interest Rate (p.a.) Comparison Rate (p.a.) Min Loan Amount Loan Term Application Fee Monthly Service Fee Monthly Repayment
IMB New Car Loan
4.99% (fixed)
1 to 7 years
$275.12 ($250 Application fee + $25.12 PPS registration fee)
You'll receive a fixed rate of 4.99% p.a.
A low minimum borrowing amount of $2,000 that you can use to purchase a new car or one that's up to two years old. - New and Dealer Used Car Loan
From 4.67% (fixed)
3 to 5 years
You'll receive a fixed rate from 4.67% p.a. based on your risk profile
Finance a new car and benefit from features such as fast approval, no ongoing fees and an optional balloon payment. Note: Settle the loan before 30 November 2020 and enter the draw to win a $1,000 fuel voucher. Terms & conditions apply.
Stratton Finance New Car Loan
From 4.05% (fixed)
3 to 7 years
You'll receive a fixed or variable rate depending on the lender you are approved with
Apply for up to $250,000 and use cash or trade in a vehicle to use as a deposit. Optional balloon payment available.
Heritage Bank Car Loan
4.89% (fixed)
1 to 7 years
You'll receive a fixed rate from 4.89% p.a.
Finance a new or used car up to 5 years old. Large maximum borrowing amount up to $100,000 and terms up to 7 years.
Credit Concierge Car Loan
From 4.45% (fixed)
1 to 7 years
You'll receive a fixed rate of 4.45% p.a. with a comparison rate of 5.29% p.a.
Get access to over 20 providers to fund a new or used car.

CUA Secured Fixed Car Loan
6.79% (fixed)
1 to 7 years
$265 ($175 Establishment Fee + $90 Security Administration Fee)
You'll receive a fixed rate of 6.79% p.a.
A secured loan with a high maximum borrowing amount up to $100,000. Redraw facility and no monthly fees.
NAB Personal Loan Unsecured Fixed
From 9.99% (fixed)
1 to 7 years
You'll receive a fixed rate between 9.99% p.a. and 18.99% p.a. ( 10.88% p.a. to 19.83% p.a. comparison rate) based on your risk profile
An unsecured loan up to $55,000 you can use for a range of purposes and pay off over up to 7 years. Note: Majority of customers will get the headline rate of 12.69% (13.56% comparison rate) or less. See Comparison rate warning in (i) above.
Symple Loans Personal Loan
From 5.75% (variable)
1 to 7 years
from 0% to 5% of the loan amount
You'll receive a personalised interest rate from 5.75% p.a. to 21.99% p.a. based on your risk profile
Borrow up to $50,000 to pay for what you need.
Driva Car Loan
From 4.34% (fixed)
1 to 7 years
$295 (Varies by lender, starting from $295)
You'll receive a fixed rate from 4.34% p.a.
Borrow up to $250,000 with loan terms from 1 to 7 years. Get access to a range of lenders.
Plenti Car Loan
From 4.89% (fixed)
3 to 7 years
from $249 to $799
You'll receive a fixed rate from 4.89% p.a.
Borrow up to $100,000 with a Plenti Car Loan and benefit from no early repayment or exit fees.

Compare up to 4 providers

Questions to ask before you buy

Would you buy the vehicle for that price regardless of the future costs saving?

If you're willing to pay the cost for the car you're getting based on its features and performance, then you're likely to be happy with it as a diesel vehicle.

Are you buying a new or used vehicle?

Diesel vehicles need to be properly maintained over their lifetime to avoid any major mechanical and engine issues. If you're buying secondhand you'll need to make sure it has no problems before you make your purchase.

How far do you drive?

As mentioned in the guide above, how far you drive has an effect on a diesel car's upkeep. If you're driving less than the national average of 15,000 km per year, or eight to ten km per day, then you may not see the fuel savings you're expecting and you may actually be worse off.

Have you secured your finance?

Remember the initial upfront costs may be higher so compare your options before you go car-hunting. Many lenders offer pre-approval so you know how much you have to spend before you buy your car. You can also consider a car loan broker that can find the loan for you.

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Car Loan Offers

Important Information*
Logo for IMB New Car Loan
IMB New Car Loan

You'll receive a fixed rate of 4.99% p.a.
A low minimum borrowing amount of $2,000 that you can use to purchase a new car or one up to two years old.

Logo for Beyond Bank Low Rate Car Loan "Special Offer"
Beyond Bank Low Rate Car Loan "Special Offer"

You'll receive a fixed rate of 4.89% p.a.
Take advantage of a competitive rate, pre-approval and no early repayment fees when you finance a car under two years old.

Logo for RACV New Car Loans
RACV New Car Loans

You'll receive a fixed rate from 4.99% p.a.
A larger loan of $5,000 or more to help you buy a new or used car. 5-hour pre approval available and no ongoing fees.

Logo for NRMA New Car Loan
NRMA New Car Loan

You'll receive a fixed rate of 4.99% p.a.
Purchase a new or used car up to 2 years old and benefit from a fixed rate and no monthly fees. Pre-approval available within 5 business hours.

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