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Tuesday 28 November 2023 Dublin: 4°C
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problem solver

Petrol or diesel - which is cheaper in the long run?

We’ve crunched the numbers on this age-old question.

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IRISH MOTORISTS LOVE their diesel cars. Last year 102,699 new car registrations were diesel-powered compared to just 40,641 petrol engined cars.

However, so far this year there seems to be a swing in the direction of petrol power. The first quarter of this year shows that petrol cars have a 29.59% market share compared to 27.97% for the same period last year and diesel cars have a market share of 66.72% which is down from 70.04% on the same period last year.

Many people believe that diesel is best due to better economy figures and cheaper tax and fuel prices – although you pay more for the car in the first place.

But is this a false economy?

Lumir Hrabcak Lumir Hrabcak

Petrol vs diesel

Let’s take a look by comparing the costs of buying and owning of a diesel car compared to a petrol car over a four-year period (the average Irish car owner holds on to their car for 3.55 years). We’ll take the Hyundai Tucson as an example as it is the best selling car in Ireland at the moment.

The Hyundai Tucson comes with one petrol engine, a 132hp 1.6-litre unit. It has a Co2 figure of 147g/km, is €390 a year to tax and has an official combined fuel economy figure of 6.3 litres/100km (44.8mpg). It has an RRP of €26,245.

According to, in Ireland in 2016, the average annual mileage travelled by a private car five years of age or less was 21,028km. The average price of petrol in Ireland in March 2017 was 136.6c a litre. Taking these figures into account, to buy and tax and run a petrol Hyundai Tucson for four years will cost €35,043.

The comparable diesel Tucson is the 115hp 1.7-litre unit. This has a C02 figure of 119g/km, is €200 a year to tax and has an official combined fuel economy figure of 4.6 litres/100km (61.4mpg). It has an RRP of €27,995.

The average price of diesel in Ireland in March 2017 was 126.0c a litre. Using these figures and the same annual mileage as above the cost to buy and run a diesel Tucson for four years is €33,670.

Therefore it is just €1,373 cheaper to buy and run a diesel Hyundai for four years.

Roger Donovan Roger Donovan

Insurance costs

But that’s not the whole story, other costs need to be factored in too. Diesel cars tend to be more expensive to insure as they have a higher value. We got one quote of €555 for the petrol model and €647 for the diesel version. This takes the difference in cost between the diesel and petrol car over the four years to just €1,005.

Service costs

Diesel cars are also, in general, more expensive to service. Hyundai’s own Complete Care plan costs €600 for five services for petrol engines and €500 for just three services for a diesel Tucson. Both plans last 100,000km or five years.

Maintenance costs

Furthermore, diesel engines are more expensive to build than petrol ones and they have more expensive parts. If something goes wrong then it is more expensive to fix a diesel engine than a petrol one.

Resale values

Diesel cars hold residual values well. Bear in mind though that is on a sliding scale – big, expensive diesel cars hold their value very well, but the gap grows smaller as the car shrinks in size with small petrol cars holding their value better than small diesel cars.

Of course, when it comes to deciding whether to go for a diesel or petrol car you have to taken into account many factors and your own particular needs – eg towing and how many motorway miles you do a year. But when it comes to overall cost, in this example it would seem there isn’t that much of a saving to be made when buying a diesel car rather than a petrol one.

READ: Car review – the Audi Q5 is rugged as well as refined >

READ: Should you buy a black car? The pros and cons >

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