Should I still buy a diesel car?

Dieselgate. NOx tax added to VRT. The rise and rise of plug-in hybrids and electric cars. Ever-more-frugal turbocharged petrol engines. There are plenty of reasons why people seem to be deserting diesel, for so long the favoured fuel choice in our country, but can you still buy a diesel car in this day and age?

New diesels: should I bother with them?

The latest diesels use AdBlue tanks of tailpipe-gas-cleaning additives and all the latest technology to make the output of their exhausts as clean as possible, in terms of NOx, carbon monoxide, particulate matter and other harmful nasties. This is because Euro 6 emissions standards, introduced in September 2015, require petrol cars to emit no more than 60mg/km of NOx, while diesels are capped at 80mg/km; in turn, this places them below the 81mg/km threshold for the highest NOx tax, and as most modern diesels emits around 43mg/km of NOx on average, then they’re below the lowest NOx tax barrier of 60mg/km. They also still emit less CO2 than petrol cars comparable for power and performance, so you’ll pay less motor tax on the diesels.

Used diesels: should I bother with them, either?

This is trickier. Used diesel imports from before 2015 are probably going to see a big hit in sales numbers here in Ireland, because they will likely incur very big NOx tax charges on VRT as a result of their exhaust emissions. You should, however, still be safe to buy second-hand diesels registered from 2016 onwards, as they will all be Euro 6-compliant and, assuming they are Irish cars in the first place, you don’t pay VRT (or, by extension, the NOx tax) on used motors.

Why would I need a diesel?

Because the quirks of WLTP economy and emissions testing are still not totally eradicated, even since the old NEDC cycle was discredited, and so plug-in hybrids (PHEVs) look a lot more economical than they actually are. While many manufacturers of PHEVs quote figures like 1.7 litres/100km and CO2 numbers well down in double digits, the reality is that they have to record these under WLTP. But, in truth, with a fully electric range of around 50km, these PHEVs do not return 1.7 litres/100km once they start using their combustion engines for any length of time. In fact, as the vast majority of PHEVs are petrol-electrics, they are much thirstier on fuel than a good turbodiesel when it comes to a long journey.

In short, there is a simple rule of thumb to determining if you need a diesel or not. If you do more than 30,000km per annum, you are going to be far better off in financial terms buying a good, solid Euro 6 diesel than you are any other car. Less than 30,000km, and you can start to look at petrol, PHEV and electric alternatives. The last two, in particular, are best suited to short-range commuters: urban and semi-urban dwellers who live in or near the cities where they work, who can regularly plug their part-electric/full-electric cars in on a daily basis to make the most of their capabilities.

So, I’m safe to buy a diesel in 2020, then?

You are indeed, as long as you pick one of the latest, cleanest models and you do a lot of kilometres on the road, each and every year. If we had to sound a note of caution, tax changes are not normally retrospective but there could be a crackdown on all combustion engines in the near future, as European governments try to shift us towards zero-emission vehicles to meet future emissions targets, but we cannot predict the future and neither can anybody else. And as, at the moment, manufacturers are still making lots of very clean and very efficient and very good diesels, you should be OK to buy one and use it for the next three to five years – at the least.