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Comment: Is our dirty affair with diesel coming to an end?

Published 10 November 2014

Most drivers react to diesel like Marmite: they don’t want to get the black stuff on their hands because it’s thick and it stinks.

It’s a futile-sounding but genuine problem. We’ve all, at some stage, filled a tank with diesel then had to endure an entire drive inhaling the chemical stench of the residual oil.

But it’s a price worth paying for the superior miles-per-gallon return that’s a given with diesel, right?

We’ll come back to that. First let’s go back in time a bit, to 1999, before the Millennium Bug ruined everything and the UK was ticking along nicely. And ticking along a lot more smoothly too, because diesel was a niche concern – the preserve of those whose main characteristic was being tighter than two coats of silver metallic. 

In a mildly harrowing coincidence, just 15 years ago diesel’s popularity was the same as UKIP’s is today – just 14 per cent.

It is, of course, highly unlikely that UKIP will follow the same statistical trajectory as diesel did from its 1999 base point, because over the following dozen years diesel sales gained huge traction, overtaking petrol sales by 2011.

The explanation for that is two-fold: prodigious technical advancement on the part of the car companies, and, as usual, some assistance from the good old taxman; diesel was already on the rise when the current CO2 emissions-based VED system was introduced in 2005, but there’s little doubt that by making tree-harming carbon dioxide the airborne enemy, rather than human-harming diesel particulates, the victory was encouraged.

Tax breaks for diesel cars was an EU-wide shtick, providing a catalyst for car manufacturers to throw the collective weight of their intellect towards the black pump. The results have been staggering in every way.

Take the Volkswagen Golf GTD, for example, which is arguably as good as the petrol-powered GTI before you start thinking about 47.1mpg vs. 67.3mpg fuel consumption. But in 1999, while GT-badged diesel Golfs were quick, they also sounded like tractors and had a power band tighter than Nigel Farage’s immigration policy. 

If it was that simple, diesel would surely continue its upward trajectory until petrol was no more. But, obviously, it’s not that simple.

The first problem is the dreaded DPF. Diesel particulate filters are supposed to cleanse a diesel’s tailpipe emissions of the aforementioned nasty toxins, which is great, except that they tend to clog up if the car they’re in spends most of its time tootling about in town. And when they clog up, then can cost thousands to replace. 

They cannot be removed either and MoTs for diesel cars now include a mandatory diesel particulate filter (DPF) check, with an automatic failure for any car found to be missing its standard filter. Therefore, a small, DPF-equipped diesel runabout can be something of an ashy time bomb.

Then there’s the fact that diesel is more expensive than petrol, and without exception manufacturers charge a premium for their diesel variants. Using our fuel cost calculator to look at the Ford Focus 1.0T EcoBoost Edge against the 1.6 TDCi Edge, for example, you’ll see that you’d have to drive 151,326 miles to make up the £1100 premium you’ll pay for the diesel version in fuel savings. Of course, the reality of paying for a car and actual mpg ratings are never that simple, but the point is valid; even using our Real MPG ratings for both cars, it’ll still take almost 45,000 to claw the initial outlay back. 

So, with diesel’s ostensibly massive economy advantage often reduced to fiction in day-to-day reality, history is beginning to repeat itself: manufacturers are turning their attention back to petrol. And funnily enough, the focus is the same: turbo technology.

Turbocharging, whose raison d’etre was first high performance in petrol cars but which later became a way of making diesels more palatable as their popularity grew, has once again became aligned to the petrol motor. This time, though, its purpose is less to force feed an engine for the sake of speed, but in order to preserve fuel.

Small capacity turbo petrol engines are fast becoming the flavor of the decade, with Ford’s EcoBoost technology a prime example: here’s an engine that, despite being a scooter-ready 999cc, can propel a big(ish) family hatchback to over 100mph and return over 55mpg.

And just to give you a personal real world example, a couple of weeks back I participated in an MPG Marathon (which is exactly as it sounds) in an Audi A3 1.4 TFSI S tronic – in other words, a turbo petrol car with an automatic gearbox, and a pretty quick runabout at that. I’m no eco driver, as you’ll know if you follow my long-term updates, but I managed 64.6mpg. Its official combined rating is 60.1mpg. 

While it was a largely deeply unpleasant experience trying to achieve that figure, it’s another telling fact that during the same event eight years ago, only one of the competing petrol cars managed to top 30mpg.

Small capacity turbo petrol technology is too nascent to detect an overall sales trend, but SMMT sales figures show that petrol sales rose last year, both actually and proportionally to diesel. Diesel’s still winning, but only just: 48.8 per cent against 49.8.

So is our affair with diesel coming to an end? Well no, clearly, but our heads are being turned.

And in any event, there’s another minority concern to think about: the 1.4 percent missing from the number above might only be a tenth as big as our last consequential niche was back in 1999, but this niche, the electric car, could feasibly kill off all fuel pumps for good.

Oh well…at least it won’t make our hands stink. 

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