Will petrol drive diesel back out?

So, how many of us made a mistake? When the then coalition government of Fianna Fail and the Greens flipped the Vehicle Registration Tax and Motor Tax systems from being based on engine size to engine emissions, the market flipped with them. We went, almost overnight, from being a people that put their faith in petrol to suddenly going ga-ga for diesel. Now, even though petrol-engined cars have made something of a small comeback, 73 out of every 100 cars bought in Ireland are powered by diesel.

Which means many of us have made a massive mistake when it comes to working out running costs. This was a point which Citroen was this week keen to make as it launched new petrol-engined versions of the C4 hatchback and C4 Cactus crossover. Shared with partner Peugeot, these new 'PureTech' engines are based around a 1.2-litre, three-cylinder architecture, with or without a turbocharger, and are conceptually similar rivals to the likes of Ford's EcoBoost engines or BMW's new 1.5-litre three-cylinder. Small displacement, big power and big claims for efficiency.

We all assumed, once the new tax regime came in, that buying diesel was going to be the only thing that made sense, and in 2008 it probably did – most petrol engined cars would have been in Bands C,D or E at best back then. Not so now though. The majority of petrol-powered family cars now occupy the ground of Bands B1 and B2, and an increasing number are slipping into Band A when it comes to tax.

That's certainly the case for the C4 hatchback using the 110hp turbocharged PureTech 1.2. That will cost you no more than €200 a year to tax, so it's only leaving you at best €20 a year better off than the diesel version. Better still, if you live in town, you'll be pumping out far, far fewer nasty pollutants – the pollutants which has Paris' mayor planning a total ban on diesel-engined vehicles entering the city centre by 2020. No wonder Citroen is keen to promote petrol once again…

In fact, according to Denis Fourchon, Chief Engineer in charge of PureTech Project, the influence to develop the engines came about 50:50 from legislation and just good corporate common sense. "I think it is both market desire and legislation which is driving a move back towards petrol. From a manufacturing point of view, it would be too dangerous to only have one foot, so to speak, with diesel, or only with petrol" he told The Irish Times. "So we have to have a good offer for both. So you look back and see the co-operation in developing the 1.6 THP engine with BMW. This was a step forward to really have a very good engine. And then in 2009 we decided to develop the PureTech range. And much of this was to protect against any potential market swing in Europe, but also it was to please the global markets.

“There will be always a gap between the two. From a technological point of view, we are coming closer and closer between diesel and gasoline engines. We are using a lot of the same technology for both. There will always be an advantage for diesel because in one litre of diesel there is a higher calorific content, so when you think about litres there will always be that advantage from the chemical composition. But besides that we are now working at the same levels of efficiency with our petrol engines.”

The figures certainly seem to bear that out. Citroen has provided us with numbers, independently verified by cartell.ie, that shows the amount of miles you would have to cover to justify driving a diesel. On a C4 hatchback, comparing the new PureTech engine and the BlueHDI diesel, you would need to cover more than 60,000km to make back the €1,050 price difference between the two cars.

it gets better, or worse depending on your point of view. If you take the C4 Cactus crossover, which has a €2,550 price gap between petrol and diesel, you’ll need to do a whopping 136,000km before you break even. And this is without even taking into account diesel’s greater likelihood of generating larger repair bills for exhaust filters and gas recirculation valves. See what I mean about making mistakes?

M. Fourchon has some words of comfort though, for those that have already taken the diesel plunge. "I hope no-one has made a mistake but what we see is that the share of the market is moving a little bit, in fact a little bit more slowly than we thought it would with the ramp-up of petrol engines. We anticipated that it would be higher by now. But maybe that's also because in some markets dealers only offer what they have sold the month before and that was diesel, so they sell it again. In France if you go into a dealer, you will see only diesel, so the customer takes what is in the showroom. So it will take time to change the market.

“Also, you have to think that on the diesel point of view, there has been a very big improvement. Diesel has not yet reached a peak of efficiency either. I think that there will always be a place for diesel, especially if you want to achieve the EU target for 85g/km average emissions. For this you need a combination of electric, gasoline or petrol and diesel especially for those who make a very high mileage per year. There will not be a unique answer, but there will be a multiple answer.”

The thing is though that it feels so refreshing to drive a medium-sized car with a petrol engine again. We’ve become so used to diesel clatter and roar that when it’s gone, you suddenly notice how intrusive it is. We sampled a C4 hatch with the 110hp engine and it was smooth, quick to rev and yet still had some of that low-down punch that diesel has acclimated us to. And it was getting almost 40mpg around town, so it would seem on this basis at least that the economy gap between the two fuels has narrowed. The engine could do with a better car to show itself off in (the C4 is a touch underrated but it’s behind the likes of the Golf, Focus and its cousin, the Peugeot 308, even with the latest round of revisions) but the inescapable fact is that many of us who should have bought petrol were railroaded into diesel.

While it’s true that diesel is a long way from dead just yet, the likelihood that the Paris ban will spread to other European urban centres should be focusing buyers’ minds rather nicely, as will the ever-increasing development cost of diesel engines, which pushes up purchase prices. Maybe, within a few years, fewer of us will be using gloves and wet wipes when we visit the fuel station…