Monday 23 April 2018

Diesel vs Petrol debate: Which option really trumps when it comes to choosing a car?

Eddie Cunningham

Eddie Cunningham

YOU could be waiting six years to get back the extra money you spend on a diesel over a petrol car, new figures show.

They reveal how you would have to drive the diesel for that length of time before it would begin to deliver savings on lower fuel and road tax.

And that’s if you do 20,000km a year. It would run to eight years if you do the national average of 15,000km. However, the timeframe does not take residual values into account.

The great petrol v diesel debate was revived by Skoda today as they unveiled their new 1-litre 3cyl petrol in the popular Octavia family car.

Read more: Revealed: Ireland's best selling car of 2016

Their research coincides with the launch of the new small engine which has can compete on performance with a 1.6-litre diesel and is more powerful and greener than the 1.2-litre petrol it replaces. There is no price increase (from €22,880 for Ambition trim) and it arrives next month.

Even though it is smaller than the 1.2-litre it replaces – and the smallest to date in an Octavia - it produces 5bhp more power than the larger engine while road tax is just €190.  It is a variation of the 3-cyl developed by Volkswagen (Skoda are part of the Group).

Basically Skoda are saying their new petrol can make more sense to thousands of people who put up 15,000km to 20,000km a year than their 1.6-litre diesel.

They frankly admit: “The new 1.0 TSI engine is so efficient that it gives the comparable Octavia 1.6 TDI 110bhp diesel engine a run for its money in terms of overall running costs.”

Read more: Revealed: The most popular secondhand cars purchased in Ireland

They are also saying that the size of engine no longer matters so much and that people need to look at power and torque (pulling power). They use the example of the first petrol in the Octavia 18 years ago. It was a 2-litre 8-valve petrol which produced 110bhp. Yet the new 3cyl, which is only half the size, produces more power (115bhp) and is way ahead on fuel consumption. And it costs only €1,300 or so more, despite being light years ahead on technology, design, safety etc. Not many things in that price range only went up by €1,300 in 18 years.

 Petrol sales evaporated here when we switched to emissions-based taxation for cars. But huge strides in engine technology have brought the fuel back to compete against diesel on emissions and fuel consumption.

The main reason for purchasing a diesel has been to get better road tax rates and savings on fuel - as diesels have had far better MPG.

Read more: 10 used cars that are worth checking out this 162-reg summer

So people paid a premium for the initially costlier diesels in the belief they would recoup the extra outlay by reducing their operating costs. But Skoda are now asking – again - if diesel is worth the extra seeing as you’d have to wait six years, possibly eight, to bridge the gap.

For the record, the new Octavia 1.0 TSI 115bhp engine uses 1.1 litres more per 100km than the 1.6 TDI 110bhp.

Another element in petrol-engine favour is the fact they tend to emit far fewer harmful NOx emissions.

So, are we on the verge of a petrol revolution? I think it will take quite a while for some people to change their perceptions. But after driving the 1.0TSI in the Octavia this morning the evidence suggests there can be real change over the next few years.

                                              Running cost comparison: Diesel v Petrol


Skoda Octavia Ambition 1.6 TDI 110bhp     Octavia Ambition 1.0 TSI 115bhp  Savings by petrol driver


Outlay (vehicle RRP)                  €25,235                                €22,880                 €2,355

Year 1 (outlay + taxes & fuels*)   €26,094                                €24,134                €1,959

Year 2 (outlay + taxes & fuels)   €26,953                                €25,389                 €1,564

Year 3 (outlay + taxes & fuels)   €27,811                                €26,643                 €1,168

Year 4 (outlay + taxes & fuels)   €28,670                                €27,898                    €773

Year 5 (outlay + taxes & fuels)   €29,529                                €29,152                    €377

Year 6 (outlay + taxes & fuels)   €30,388                                €30,406                     -€19

*Assumes petrol @ €1.27 and diesel @ €1.13. Annual road tax €190 for 1.0 TSI and €180 for 1.6 TDI

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