It’s been a rough few years for the diesel engine. It wasn’t long ago that modern diesel engines were being hailed as the super-efficient, low-consumption, low-emission engine of choice. So much so that for the first time ever, diesel engines overtook their petrol counterpart, claiming over 55% of all global car sales back in 2011. A lot’s happened since then, so UK DPF Cleaning takes a look at the good, the bad and the ugly side of diesel cars and whether you should still consider buying one in 2022.

A brief history of the Diesel Engine

Invented by scientist Rudolf Diesel back in the 1890s, diesel engines were only introduced into modern motor vehicles in the 1930s. At this point, they were used almost exclusively to power commercial or heavy-duty vehicles that required high power at low speeds. This made diesel engines ideal for agricultural and logistical vehicles such as tractors, heavy goods vehicles or trucks. 

Fast-forward to the 1990s and after some early success by manufacturers such as Peugeot, Mercedes and BMW, diesel engines started to eat away at the consumer market share that belonged almost exclusively to petrol vehicles. Diesel engines could finally offer the same kind of performance, power and durability as petrol engines whilst also offering motorists improved fuel consumption. By 1992, diesel cars represented 17% of all car sales in Europe. 

In the years that followed the phrase ‘Climate Change’ first came to the fore as scientists began to understand the negative effects rapid industrialisation and commercialisation of major nations was having on the environment. Global leaders took note and encouraged the purchasing of diesel vehicles through lower road tax, as diesel engines had since proven to produce fewer CO2 emissions than petrol engines. 

By 2011, for the first time ever, diesel engines overtook petrol engines in like-for-like sales around the world. Lower taxation, better fuel economy, cleaner emissions. It was easy to see why diesel cars became the car of choice. 

So what changed and why is ‘diesel’ a dirty word again? 

September 2015. ‘Dieselgate’ hits the headlines. Unquestionably, the single biggest scandal in vehicle manufacturing history. Otherwise known as the ‘Volkswagen Emissions Scandal’, ‘Dieselgate’ kicked off when the United States Environment Protection Agency issued a notice of violation of the Clean Air Act to German vehicle manufacturer, Volkswagen Group. 

They had discovered that VW, who also produces Audi, Skoda, and Seat vehicles, had used special software during regulatory emissions testing to record fraudulent emission figures. In some cases, the real-world driving emissions were up to 40 times that of the ones stated to regulators during ‘factory-testing’. 

What followed was one of the largest class action lawsuits ever recorded with over 90,000 successful claimants costing the VW Group in excess of $25 billion dollars and counting. 

Suddenly diesel engines were being scrutinised for being less friendly than they were perhaps once thought. Whilst diesel cars do emit fewer hydrocarbons, carbon monoxide and lead pollution than petrol cars, they are known to emit more noxious gases along with particularly nasty particulates that have been linked to respiratory health problems across the planet. 

The debate however continues to rumble on as to whether petrol or diesel cars are more harmful to the environment. Many newer diesel cars have been proven to produce fewer emissions than their petrol-drinking competitors but regular maintenance of said diesel vehicles is imperative to maintaining lower levels. 

So… should I still buy a diesel?

There’s no reason why you shouldn’t consider a diesel when buying a car BUT they may be better suited to some motorists over others. 

To combat the harmful particulates that diesel engines emit, in 2007 the Euro 6 standards dictated that all manufactured diesel vehicles must be fitted with a DPF filter. A DPF filter is similar to the catalytic convertor found on a petrol car in that it captures some of the harmful exhaust emissions and prevents them from entering the environment (Find out more about DPF Filters here). DPF Filters help to catch the harmful particulates that would otherwise enter the environment and ‘burns’ them into ash. This process is called regeneration. Regeneration requires a couple of key conditions to work effectively; High speeds and long running time. 

In order to ‘burn’ the particulates, the DPF filter must reach a certain temperature in order to produce enough heat. To do this, the vehicle needs to drive at a relatively high speed (50-60mph+) for a long period of time (Over 30 minutes). If the vehicle doesn’t reach high enough speeds over a long enough period of time regeneration process won’t begin and the harmful particulates left from burning diesel fuel will remain inside the filter, leading to a clogged filter. 

This means that motorists considering a diesel vehicle should think about the typical journeys they make and projected vehicle usage. If you only make short journeys, i.e. drop the kids off at school in the morning or pop to the local shop a couple of times a week, a diesel vehicle may not be for you.

Diesel vehicles are most efficient for motorists that make long journeys or commutes, frequently and along stretches of motorway or dual carriageway. These motorists will also benefit most from the superior fuel consumption offered over petrol engines. 

Why else might I still opt to buy a diesel?

Diesel engines are excellent at producing high torque/power at low speeds making them ideal for towing trailers, caravans or other heavy loads. (That’s also why most commercial vans, which have to carry heavy tools and materials, have diesel engines.)

Key reasons to buy a modern diesel car over petrol

  • You drive over 15,000 miles annually
  • The typical journey time is over 15 miles
  • The typical journey includes motorway/carriageway stretches
  • You tow heavy loads, i.e caravan, trailer etc

Will diesel vehicles be banned?

The future of diesel engines was decided in 2021. The Government confirmed that the production of diesel and petrol combustion engines would be banned from the year 2030 with an aim to reduce carbon emissions and reach ‘net zero’. However, this doesn’t mean that diesel engines will be banned from use until long after 2030. Anyone buying a diesel vehicle now should not worry any more than those buying a petrol vehicle that they will suddenly be banned from driving it… unless you’re area is under consideration for ULEZ expansion!

The new law bans the production of the diesel engine (as well as the petrol engine) but does not state in any way that diesel vehicles will be banned from UK roads altogether. 

What to look out for in a diesel vehicle

Despite all the bad press in recent years, diesel engines still have their place on UK roads and motorists shouldn’t be deterred from buying second-hand diesels providing they have been well looked after. 

Always take a car for a test drive where possible and make sure everything is running smoothly as you would a petrol car. In particular, check the dash for any warning lights or messages that might indicate the DPF is full or blocked. If you’re not sure about what to look out for on a second-hand vehicle, companies like RAC offer vehicle inspections (at a cost) on second-hand vehicles prior to purchase (Check with the seller first but if they have nothing to hide they shouldn’t have any objections).

Also check the vehicle service book for the main dealership, or recognised service station, service stamps. These should be carried out annually. Be wary of older cars with a patchy or non-existent service history. 

Avoid diesel vehicles that feel ‘rough’ or ‘bumpy’ whilst idling. Whilst not all diesel vehicles carry turbos, many of them do, so on your test drive, try to check that the turbo kicks in correctly at different speeds.