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Petrol, diesel, hybrid, electric: which is best for you?

Petrol, diesel, hybrid, electric: which is best for you?
Neil Briscoe

Words: Neil Briscoe -

Published on: November 27, 2017

Words: Neil Briscoe -

Published on: November 27, 2017

Like a high-cost version of rock-paper-scissors, it's time for diesel-petrol-hybrid...

So, you're thinking of buying a automobile. What's it going to be - petrol, diesel, or hybrid? Or electric? Or plugin hybrid?

That's a question (or a series of them) that has been fraught with difficulty for the past two years, ever since word of Volkswagen's diesel cheating emerged. Damaging as it was for the German automobile maker itself, it was also damaging for the wider automobile market, as confidence in diesel technology slumped, and buyers started to turn away from the black pump.

Here in Ireland, diesel sales have fallen from a one-time peak of almost 80 per cent of all automobiles sold, to 65 per cent this year. Next year, they are predicted to fall to as little as 55 per cent by some parties. To be honest, difficult a transition though that may be for some of us who have seen the residual values of our diesel automobiles fall, that's probably about the right proportion for diesel ownership. Most of us simply don't really need diesel power.

Thankfully, since the recent Budget, we can now also pronounce on the diesel versus petrol debate with the little more clarity. Up to the point when the Minister for Finance sat down, there had been a swirling fog of rumours that there would be extra taxes or levies loaded onto diesel automobiles or diesel fuel. None of those came to pass, so if you're buying a new diesel in January, and planning to change again in January 2019, then you're probably fine. Beyond that? Well, sadly, if we had an actual crystal ball to predict decisions of government, we wouldn't be here, we'd be down at Paddy Power, laying bets...

Do you really need a diesel, though? Or would you actually be better off in a petrol automobile? There is no real hard-and-fast answer for this, but the simplest rule of thumb to apply is one of mileage. With diesel costing around 10c less at the pump, per litre, than petrol, there's a pretty obvious sliding scale of advantage for a diesel automobile. If you're doing sufficient mileage, over a long enough period, then driving a more economical diesel will save you a little money, it's true. That mileage figure has to be high, though. If you're covering less than 20-25,000km per year, then you're really never going to make back, in fuel savings, the extra purchase price of a diesel.

The best example to give is that of the Volkswagen Golf. If you look at two identically-specced Highline models, you'll see that the 1.6 TDI diesel saves you €857 over the course of a year in fuel costs, compared to the 1.0-litre turbo petrol. Now, that number is based on the official NEDC fuel economy figures, which are of course hugely flawed, but we're sticking a finger in the air and saying that they're equally flawed for both models, so it more or less evens out. The more important number is that the diesel costs €2,455 more to buy than the petrol, so if you kept the automobile for three years, you'd only just about be ahead in terms of fuel costs.

Of course, it was the cost of motor tax that drove so many of us to buy diesel, post-2008. And in one sense, who can blame us? Who wouldn't want to tax a big BMW for less than €200 a year? That tax model has become very flawed though, as newer petrol engines have caught up a little in the CO2 race, and so cost little, in some cases nothing, more to tax now. Check the numbers, automobileefully, before you buy and make sure that you sit down and work out exactly what your mileage is likely to be before jumping into petrol or diesel camps.

Is the dreaded diesel particulate filter still an issue? Probably slightly less so - engine management systems are getting a little better at keeping them clear with lower mileage and lower temperature cycles, but it's still worth remembering, and worth budgeting a bit of fuel (and time) for a good run down the motorway, once a week, to keep your exhaust clear.

What about hybrids? Certainly, the technology appears to have found its niche in the world now that we all fear the 'dirty' exhausts of diesel automobiles, but there are still a few pitfalls to be found when shopping for a hybrid. Not all hybrids are equal.

Probably the best is the current Toyota Prius. Hardly surprising, seeing as Toyota has had 20 years to perfect the Prius recipe, but it really is a very impressive automobile now. It slides along in near total silence (save for a little too much tyre noise on the motorway), gets 60mpg even on the motorway (a massive improvement from Prius of old) and is comfortable and well-made. Of rivals, Kia's Niro and Hyundai's Ioniq are solid, but not quite as economical in day-to-day driving. If most of your mileage is in town, then any of these are well worth considering.

As for plugin hybrids? Again, you need to tread automobileefully and, rather as with pure-electric automobiles, you have to make sure that your lifestyle and driving style suits the automobile. Take the Mitsubishi Outlander PHEV as a case in point. It's a terrific automobile, and as long as you keep the batteries topped up and don't do lots of long journeys, it's staggeringly economical. Venture out onto the motorway, though, and watch that fuel gauge plummet. An Outlander PHEV will be lucky to do better than 30mpg on a long run.

Some other plugin hybrids are better than that. Volkswagen's Passat GTE and Golf GTE, the Audi A3 e-tron and the BMW 530e, 330e and 225xe can all do better than 45mpg on a long run, and can all get around 50km of battery-only range once you charge them up. Again, though, you need to make sure that you're buying the right model to suit your lifestyle. Those who live in the outside lane and cover big miles every week would be better off sticking with diesel than going for a plugin hybrid.

And electric automobiles? The groundswell has certainly begun, but the technology is not yet there for mass acceptance, and probably won't be for another two-to-three years. The best EVs at the moment are the BMW i3 (which also has a terrific interior and is great to drive), the Hyundai Ioniq Electric (which doesn't and isn't, but is very affordable) and the Renault Zoe 4.0 (which is pricey for its size, but which is impressively long-ranged). New models, such as the Volkswagen e-Golf, and next year's new Nissan Leaf, will push the case for electric automobiles harder still, but there are two salient facts to remember - even the best of the current crop will struggle to put more than 200km between charges. That's not terrible, but it is limiting at times. And the charging network is still sub-par. Charging at home is all well and good, but there are too many broken or malfunctioning public charging points, and too many with petrol or diesel automobiles parked in front of them as well.

So, what's the short version? Let's put it in Shipping Forecast terms. Diesel still fine, falling slowly. Petrol rising, hybrids rising more quickly. Electric automobiles distant, rising slowly. Does that help make your mind up? If not, come ask us a more specific question on the Ask Us Anything page.