The burning question: diesel, petrol or hybrid?

With 181 registrations looming, the question of how to fuel your next car becomes critical

Diesel or petrol: which one best suits your driving habits? Photograph: Getty Images/EyeEm

Diesel or petrol: which one best suits your driving habits? Photograph: Getty Images/EyeEm


Petrol or diesel used to be a question with a pretty simple answer – diesel for business or long-distance drivers, petrol for everyone else. The Government turned that equation on its head in 2008 with the Co2-based VRT and motor tax system, and suddenly it was diesel for all.

Then, two years ago, Volkswagen grabbed hold of the same equation and shook it until some deeply worrying numbers, and indeed headlines, began tumbling out. Diesel became evil overnight, just as electric and hybrid cars began to gain, at little, ground. As we approach January 1st and the kick-off of 181 registrations, the question is, which one is right for you?

First off, it needs to be said that although electric cars have been riding high in the headlines lately, they remain very much a minority interest case. Not only is there still but a handful of electric cars on sale (in fact there are just nine pure-battery powered electric vehicles on sale in Ireland right now, and that’s being charitable and including such as the oddball Renault Twizy and the van-only Renault Kangoo ZE) and they are all, to a car, savagely more expensive than an equivalent petrol or diesel (excepting the most basic version of the Nissan Leaf). So is battery power truly viable for us all? We shall see…

Does diesel still make sense?

In the meantime, it’s time to measure the notional piece of string. The first question is surely diesel or petrol, as those are still the dominant forces in the market accounting for, respectively, 65 per cent and 30 per cent of the total car market. Diesel has taken more than a few hits this year, in terms of both public image and actual sales, but almost surprisingly, Minister for Finance Paschal Donohoe stayed fiscally silent on the issue in the budget, and there was none of the potential punitive extra diesel taxes and levies that had been half-expected, all-feared.

So, does diesel still make sense? Yes, if you cover sufficient kilometres which has always been the answer (and which we all ignored in 2008). Should you be worried about diesel particulate filters (DPF) and their tendency to clog if you don’t cover enough distance every day? Also yes, and they can be searingly expensive to fix, but the secret is heat. If you’re a short-distance daily driver with a diesel, just make sure you go for a good strop along the motorway or nearest main road once a week, keeping the revs up, which will build up the heat in the exhaust and clean out the DPF.

The mileage also decides whether it’s worth paying the extra price at purchase time over and above a petrol engine, but most diesel buyers already realise that – according to the Central Statistics Office, an average buyer of a 1.6-litre diesel-engined car covers some 24,302km every year. That’s just about enough to claw back the extra spent on purchasing the car in fuel savings. Just.

Ah, but should you be worried about the environmental impact? Well, the question is actually which environmental impact? You see, there are two. Diesels do, unquestionably, affect local air quality and the noxious emissions of nitrogen oxide (NOx – the gas that tripped up VW’s emissions tests and exposed the cheating) are without question a perilous danger to public health, not to mention the carcinogenic properties of diesel soot (or particulates, hence the filter).


But, if you are buying a new diesel, then it conforms to Euro6 emissions regulations, which with the addition of AdBlue (basically uric acid, and yes we all know where that comes from…) all but eliminates the emissions of NOx. According to Martin Dunne, technical manager with Peugeot’s Irish importer, Gowan Distributors, “with our third-generation filters and the SCR [that’s the AdBlue injection], I would be saying that our diesels are as clean, at the exhaust, as our petrols.”

Paulo Alves, managing director of BMW Group Ireland, echoes that point. “There’s a concern among consumers about diesel,” he said in an interview at the Predict Conference. “There’s a lot of worry about diesel from an emissions perspective but we believe that there is still a strong demand for diesel, and actually we welcome some of the disruption. Why? Because buyers are now looking more objectively at what suits their needs. If you’re a high-mileage driver, then diesel is still for you, and with a Euro6-compliant car, it’s as clean as a petrol car.”

Can we trust such assurances? Well, we don’t really have a choice – the cars do conform to the current legislation, so they’re approved for sale at a European level. At that point, it’s up to our representatives on the European Commission and in the European Parliament to ensure proper compliance.

Will you get stung on depreciation with a diesel, though? Ah, that’s a very good question. The answer is... it depends. You see, there’s a distinct urban/rural split in diesel sales at the moment. With all of the adverse publicity surrounding diesel emissions in towns, urban buyers are fast switching back to petrol, or defecting to hybrids. So if you live in town, then you’re probably going to find that your diesel will be trickier, at best, to sell on in two to three years’ time. If you’re living down the country, then you’re probably fine in that sense, at least for now and at least until the motor tax system is revised again. One word of warning though: second-hand diesel prices in the UK are falling, and fast, and the Brexit-driven tide of UK imports is driving down prices here across the board. And depreciation is the biggest single cost of motoring.

Ah, but you say, surely petrol engines have improved in the past few years and can now challenge diesel head-on? Yup, pretty much, although again it does depend a little on the mileage. In general, we would suggest that the likes of VW Group’s 1.0 and 1.2-litre TSI petrol engines, Ford’s 1.0 and 1.5 EcoBoost, Peugeot and Citroen’s 1.2 PureTech, Hyundai and Kia’s 1.0 T-GDI and others can all, mostly, match their diesel peers for overall economy, or at least get close enough that the diesel driver isn’t going to make back the extra cost of purchase in fuel savings. As an added bonus, every one of those engines is sweet to drive, and makes pleasant burbling noises, should such things matter to you.

Trading up

Even when trading up to larger cars, petrol can still make sense. A BMW 320i can be, if driven gently, near as damn it as economical as a 320d, and the same goes for an Audi A4 1.4 TSI, or Mercedes-Benz C-Class, either 180 or 180d. That said, if endless motorway miles are your daily grind, then diesel is still king, and at least you’re not choking up town centres with your exhaust.

So where does hybrid come in? Hybrid sales are up by some 79 per cent so far this year, to 4,343 cars, and the bulk of that has been taken by two models – Toyota’s C-HR and Prius (with the little SUV taking, by far, the lion’s share). This is, obviously, partially driven by the diesel dilemma, but also by the fact that Toyota has at last refined its hybrid systems to the point where they work properly. Previously, if you took an old-shape Prius on the motorway, you were lucky to see the sunny side of 30mpg. Now, with the current (somewhat visually challenging) model, you’re looking at an easy 60mpg, maybe more.

So, what’s the answer? Well, the short version is what it’s always been: diesel for high-milers, petrol for everyone else. Now too, we have the addition of hybrid for those who fancy something a little more interesting. And what of plugin hybrids and even electric cars? Ah, that is all another story…


Let’s take three of the best-selling cars in Ireland and see if it makes more financial sense to buy petrol or diesel. Please note, we’re leaving insurance costs out of this as the loading is more on the driver than the car and we’re going to assume average mileage of 20,000km per year – half way between the average figures for petrol and diesel users.

Hyundai Tucson. Ireland’s best seller of all, right now.

Diesel: 1.7 CRDI Executive. €30,995. Claimed economy: 4.6l/100km. Emissions: 119g/km. Tax: €200

Petrol: 1.6 GDi Comfort. €26,245. Claimed economy: 6.4/100km. Emissions: 144g/km. Tax: €390.

Okay, so we’re not quite comparing apples with apples here – the Tucson’s petrol engine is only available in the most basic Comfort trim, while the best-selling model is the Executive diesel. So you will have to sacrifice quite a few features to save €4,650 on the purchase cost. You’ll have to use that to fund an extra €570 in motor tax over three years.

On fuel, assuming you’re getting the official combined figure (you won’t but this is for comparative purposes), you will burn through 2,760 litres of diesel over the three years, which, at today’s average pump price of €1.22, will cost you €3,367.

The petrol, by contrast, will need 3,840 litres of juice (again at the official combined economy rate – pure fiction, this) costing you €5,145 at the current average pump price of €1.34.

So, the total petrol costs are car price (€26,245) plus tax (€390) plus fuel (€1,715, for one year), which equals €28,350. That’s a significant saving over the diesel’s total cost of €32,317 but it does leave out subjective (and quantitative) differences between trim levels and the contrast between a very decent diesel engine and a very ordinary petrol one. The diesel gets the nod here, just.

Volkswagen Golf. Ireland’s best-selling family hatchback.

Diesel: 1.6 TDI Highline. €30,825. Claimed economy: 4.1l/100km. Emissions: 106g/km. Tax: €190.

Petrol: 1.0 TSI 110hp Highline. €28,370. Claimed economy: 4.8l/100km. Emissions: 109g/km. Tax: €190.

When we come to the VW Golf, the best-selling family hatchback on the market right now, the gaps are much closer, yet still petrol pulls out an advantage.

By going for the diesel model, you’re saving yourself a mere €857 over three years on fuel costs (€3,001 for the diesel, €3,858 for the petrol) but there’s a purchase saving of €2,455 and the cars are identically-specced, and there’s no difference in their tax costs. Added to which there’s the subjective element that the new 1.0-litre TSI petrol engine is a delight to drive, and far sweeter on the ears than the 1.6 TDI. A big win for petrol, here.

BMW 5 Series. Ireland’s best-selling executive car.

Diesel: 520d M-Sport. €51,950. Claimed economy: 4.5l/100km. Emissions: 109g/km. Tax: €200.

Petrol: 530i M-Sport. €64,750. Claimed economy: 5.8l/100km. Emissions: 132g/km. Tax: €390.

Let’s get this out of the way with – it’s an easy win for diesel here thanks to the fact that, for now, there is no direct petrol equivalent of a 520d. Until a new 520i arrives, there’s only the option of a far more expensive and powerful 530i.

Just for the sake of it, the petrol car costs €12,800 more than the diesel, will need an extra €1,369 worth of fuel over three years, an extra €570 in tax and doesn’t even have a six-cylinder engine anymore to help you justify the extra. Mind you, when the 520i does arrive, this could well all be turned upside down.

*In Motors on January 3rd – Opting for alternatives: hybrids or electric?

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