Triumph to disaster: the rise and fall of diesel

Diesel cars have been popular in Europe for decades – while Asian and American buyers have largely shied away from it.

Now it looks like diesel is approaching the end of the road even in Europe, at least for mainstream passenger cars. These are the highs and lows of diesel, since the first patent was filed almost 130 years ago.

The first patent (1890)

The first patents for a compression-ignition engine were filed by the Briton Herbert Akroyd-Stuart in 1890; by 1891 Richard Hornsby & Sons had bought the patent and was producing hot bulb (or heavy oil) stationary engines. These engines were the first to use a pressurised injection system, with combustion taking place in a separate chamber rather than the cylinder.

Diesel files his patent (1892)

The man behind the diesel engine as we know it was the German Rudolf Diesel. Born in 1854, he filed his first patents in 1892 and within five years he had a working engine. With his engines, air and fuel were injected into the combustion chamber; with Akroyd-Stuart’s design, only fuel was injected. Diesel’s design also featured a much higher compression ratio to maximise thermal efficiency.

Diesel is much less volatile than petrol/gasoline. Instead of igniting the fuel/air mixture with a spark, as in a petrol engine, the fuel in a diesel engine is compressed until it ignites. That’s why the compression ratio in a diesel engine is so much higher than in a petrol unit; it’s also why diesels have that distinctive rattle. One of the reasons why diesel engines have got quieter is because compression ratios have dropped, from around 25:1 to typically more like 14-16:1.

Diesel’s demise (1913)

In 1912 the first diesel-powered ship went into the service, the Selandia; two years later the first diesel-engined locomotives began plying their trade in Germany. In the meantime, in September 1913 Rudolf Diesel was on a cross-Channel ferry to England when he disappeared, never to be seen again; did he jump or was he pushed?

Peugeot Type 156 25HP (1922)

The first diesel-powered car was a 25HP Peugeot, into which a Tartrais-designed diesel engine had been installed. It was a one-off rather than a production car, but it worked and could get all the way to 43mph while returning a positively parsimonious 18 miles per gallon. A year later, Mercedes launched its first diesel-engined lorry with indirect injection; rival MAN launched a lorry with direct injection in 1924.

Citroen Rosalie (1935)

During the 1930s Citroen worked with Ricardo to create oil-burning versions of its cars, but all were prototypes including a Traction Avant. More charming though was the Rosalie, which was offered for sale in Europe on a limited basis. Two years earlier, British company Gardner introduced a diesel engine for automotive use, but it didn’t offer complete cars, just powerplants to convert petrol vehicles to diesel.

Mercedes 260D (1936)

Mercedes and Peugeot were the biggest players in diesel-car development in the early years. The first diesel-powered production car was the 260D of 1936, the 45bhp model achieving 60mph; they were popular with taxi drivers.

Peugeot 402 (1936)

Just pipped to the post by a matter of weeks, Peugeot was the world's second company to offer a diesel-powered production car. The 402 was pretty good too, as it was capable of a genuine 60mph, but it was far too costly for most buyers.

Mercedes 170D (1948)

After the war it was Mercedes that was the quickest to develop and introduce diesel power for its regular passenger cars. Its 170D offered a meagre 38bhp with a rough tickover, but 62mph was possible along with 32mpg.

Standard Vanguard (1948)

When the British Standard Vanguard was unveiled in 1948, there were sharp intakes of breath for this all-new car with US-influenced styling. 

Standard Vanguard (1948)

But there were few takers for Britain’s first diesel-engined production car which was rough and slow. Peak power was pegged at just 40bhp.

Diesel racer ‘success’ (1952)

America's Cummins Engine Company entered a diesel-engined Duesenberg in the 1931 Indy 500 and while it finished, it did so way down the field. In 1952 Cummins returned, this time with a turbocharged 6.5-litre straight-six, where incredibly it qualified in pole position. But on the 52nd lap the car was forced to retire when the turbo failed. Cummins is today one of the world's largest producers of diesel engines.

Borgward Hansa (1953)

One of the earliest reviews of a production diesel car that Autocar ever published was on the Borgward Hansa. Launched in 1953 in Britain, the 1.8-litre small saloon was priced at a hefty £1481 (US$4144 at the time) – at a time when a Ford Consul could be yours for £666 while a Zephyr-Six was pegged at £754. A year later, Volvo put the first turbodiesel truck into production.

Peugeot 403 (1958)

Until now, diesel-powered cars had been for those wanting something that would cover massive mileages without needing a rebuild, but at a big premium. The Peugeot 403 changed that, as this 1.8-litre car was much more affordable than its predecessors.

Austin FX4 (1958)

London’s taxi drivers didn’t care all that much about performance or refinement; what they craved was economy with longevity, and that’s exactly what Austin’s 2.2-litre engine delivered. Fitted with a Borg Warner automatic transmission, the FX4 could rack up hundreds of thousands of miles before a fresh powerplant was needed.

Rover P4 (1960)

Rover didn’t offer a diesel engine in its P4, although with its four-cylinder diesel unit being based on the petrol engine, swapping from one to the other was easy enough. As reported in our 11 March 1960 issue, one P4 owner chose to swap his six-cylinder petrol engine for a four-pot diesel, so he could enjoy caravanning without being crippled by the fuel costs.

Austin Cambridge (1961)

Although diesel car sales were absolutely miniscule at a global level in 1961, for some reason the British Motor Corporation decided to start offering an oil-burning Austin Cambridge, equipped with all of 40bhp from its 1489cc.

Austin Cambridge (1961)

It was a sales disaster.

Austin vs Hillman (1963)

In our 1 February 1963 issue we published our first ever diesel twin test, comparing the Austin Cambridge with the Hillman Super Minx; the latter had to be bought in petrol form, then converted by Perkins to diesel. Unsurprisingly the Austin won, as it came with diesel power ready to go.

Peugeot 404 (1966)

Starting out with a 404 cabriolet, Peugeot created a diesel-engined record breaker with a fixed narrow roof and just 69bhp. It ran for 72 hours at Montlhéry, breaking 22 speed records in the process, three of them all-new.

Peugeot 204 (1968)

Because diesel engines are inherently less powerful than petrol units of a similar capacity, they tend to have larger displacements (or a turbo). But this Peugeot's 46bhp engine displaced just 1255cc; it was the world’s smallest diesel engine and it marked a turning point for diesel power as the 204 was more popular than anything that had come before.

Mercedes 240D (1974)

The W115-based 240D appeared at the end of 1973 with a 2.4-litre four-cylinder engine. Less than a year later Mercedes added an extra cylinder to create the 240D 3.0, or in the US the 300D – the world’s first production five-cylinder diesel car. It was rated at just 77bhp while fuel consumption was pegged at all of 21.5 miles per US gallon, equivalent to 26mpg in Europe.

Cadillac Seville (1975)

More a low point than a highlight, but the V8-engined oil-burning Cadillac Seville is worth a mention simply because it was decades ahead of its time, even if it was a sales disaster. It would be another quarter of a century before buyers in the luxury segment would latch onto diesel, and even then only really in Europe.

Volkswagen Golf (1976)

We were fascinated by the Golf diesel, which attempted to bring the fuel into the mainstream. We ran a technical analysis of its engine, reviewed it several times and in 1979 ran one on our long-term fleet. We managed to squeeze 64mpg out of it (but averaged 51.4mpg), after running the car for 24,000 miles.

Mercedes 300 SD (1977)

Although forced-induction diesels had been built decades before, this was the first one put into series production and offered as a regular model. The 300 SD was powered by a three-litre five-cylinder engine but it was offered only in the US.

Citroen CX (1977)

We ran our first diesel long-termer in 1977 – a 2.2-litre Citroen CX. Over 18,000 miles we averaged 33.5mpg and loved the car’s long-legged cruising abilities. While petrol-engined CXs got a rev counter, diesels didn’t “because with no ignition to drive a rev counter, Citroen has no choice”.

Mercedes C-111 (1978)

The Mercedes C-111 concept car was powered by a three-litre supercharged five-cylinder diesel engine and averaged 198.7mph over 100 miles and 195.3mph over 12 hours. Running at the Nardo test circuit in Italy, it claimed a raft of records, including eight for vehicles with any type of engine.

Peugeot 604 (1979)

With the Americans suddenly all fuel-conscious, Mercedes had launched its 300SD only for the US market, leaving Europe wide open. Peugeot seized the opportunity and was first to sell a turbodiesel car in Europe, the 604. The 2.3-litre engine produced just 79bhp. Hauling around a 4720mm (186in) long, 1465kg (3230lb) luxury car, performance can best be described as relaxed, with 0-60 dispatched in 16.5sec. It proved reluctant to start in cold weather, and thus parking on a nearby hill was advised, if available.

The diesel was exported to the US in 1981, but didn't sell well. 

Volkswagen ARVW (1980)

The Aerodynamik Research Volkswagen was built with one aim; to shatter as many diesel speed records as possible, many of them set by Mercedes' C-111. The 173bhp single-seater ARVW notched up nine records in all.

Mercedes 190D (1982)

Diesel-powered cars had always been much noisier than their petrol counterparts, but Mercedes aimed to change that with the 190D. This was the first diesel car to have its engine fully encased, for better refinement.

PSA’s XUD engine (1982)

In 1982 PSA introduced its XUD engine, which would go on to power a multitude of cars including Citroen’s BX, Xsara, ZX and Xantia among many others, while Peugeot fitted the XUD to its 205, 309, 405 and much more. For years it was the most successful diesel engine available, largely because rivals were slow to offer their own diesel-powered cars.

Talbot Horizon (1982)

The first recipient of the XUD powerplant was the Talbot Horizon. The original plan had been to build a turbocharged 1220cc diesel engine, but in the end Talbot decided it was easier to just stick in a much bigger normally aspirated unit. The result was a 1.8-litre engine, which delivered 65bhp. We drove it in January 1983; we concluded it was 'quick for a diesel.'

Daihatsu Charade (1983)

This was a real oddity; Japanese firms were very slow to offer diesel cars, but Daihatsu offered an oil-burning Charade as early as 1983. It was powered by a three-cylinder engine in normally aspirated or turbocharged guises.

ELKO engine (1983)

When we tested a Mercedes W123 estate in 1983 fitted with an Elko diesel engine, we thought a diesel revolution was just around the corner. This 1386cc three-cylinder engine allowed the Merc to cruise at 102mph in comfort, ran on vegetable oil and was so efficient that it didn’t need a radiator for cooling. But the engine was too costly to build for it to be adopted by a mainstream car maker.

Peugeot 205 (1984)

It was arguably the 205 which brought diesel power to the masses in Europe, thanks to its relative affordability, reliability, economy and Peugeot's long-standing reputation for producing seriously great oil-burners.

Range Rover 2.4D (1986)

The BBC was meant to support British industry, but the VM-engined Rangie was so awful that Top Gear had to slate it. BL complained, the BBC stood its ground and a new era started for Top Gear, with criticism allowed.          

BMW 324td (1987)

Electronic management systems have transformed engine efficiency and for diesel engines this is where it all started; the BMW E30 was the world’s first production car with electronically controlled fuelling. The car was sold in continental Europe only, with no right-hand drive cars produced.

Fiat Croma (1988)

Now forgotten, three decades ago Fiat introduced the world’s first series production car with a direct-injection diesel engine. Shortly after, Audi introduced its own first direct-injection diesel engine, placed in the Audi 100.

Citroen AX (1989)

For those wanting to keep their fuel bills to a minimum, the diesel AX was a dream come true. Not only was it easily possible to average 60mpg in everyday use, but in 1989 it broke the Guinness World Record for the most frugal production car available; the tiny Citroen could manage a deeply impressive 112mpg.

Citroen XM (1989)

Although multi-valve petrol engines had been around for decades, the XM D Turbo of 1989 was fitted with the world's first multi-valve diesel powerplant. It was fitted with just the one exhaust valve, but a pair of inlets.

Volkswagen Golf (1990)

Catalytic converters wouldn’t become mandatory across Europe until 1992, but two years earlier Volkswagen introduced them on its Golf Umwelt (Environment). This was the first diesel car to be equipped with a two-way catalyst. A year later the German company produced a diesel/electric hybrid prototype.

Westfield ‘Weasel’ (1992)

The idea of a diesel engine in one of the purest and most lightweight driver’s cars ever might seem ludicrous, but when Richard Wilsher slotted a 1.8-litre Ford turbodiesel engine into the nose of a Westfield it didn’t seem at all stupid. Especially when it could accelerate faster than a BMW M3 Evo or Porsche 928 S4.

BMW 525 TDS (1993)

On paper this was just another six-cylinder oil-burner, but it didn't take much driving to tell it was something special. A cut above the 525 TD that was offered alongside, the TDS was the world's best diesel when it debuted. The TDS was good for 139bhp and 192 lb ft of torque.

Mercedes-Benz C-Class (1993)

Petrol engines with four valves per cylinder had been all the rage through the 1980s, the technology having been pioneered by the Triumph Dolomite Sprint of 1973. Two decades after the Triumph arrived, Mercedes put the world’s first diesel engine with four valves per cylinder into production, in the C-Class that arrived that year.

Diesels blow up (1993)

In January 1993 the UK government introduced new rules for the 'MoT' annual test for cars over three years old.  The new test involved revving an engine to its maximum governed speed 10 times in quick succession. The problem was that engines started to go pop, forcing a rethink.

Aston Martin DB7 (1994)

The arrival of the DB7 marked the start of a new era for Aston Martin, but offering a diesel engine in its new GT was perhaps going a step too far. That didn’t stop the company talking about it though, as we reported in March 1994.

Alfa Romeo 156 (1997)

Common rail fuel delivery is the norm nowadays, and has been for years. But it was the Fiat Group that blazed a trail with the technology, in the Alfa Romeo 156. The tech ensures the fuel injection timing, quantity of fuel and atomisation are controlled electronically using a programmable control module. This allows multiple injections at any pressure at any time to give the optimum balance of power, fuel consumption and emission control.

Smart ForTwo CDi (1999)

Small cars don't usually have diesel options because the price premium is too great. Try telling that to Smart though, which introduced a 799cc oil burner in 1999, in its Coupé. Some French quadricycle manufacturers were offering even smaller diesel engines at the time; Ligier and Microcar both offered 505cc two-seaters for example.

Fiat NZEV (2000)

Fiat announced in 2000 that it was working on a 1.2-litre 16-valve Multijet diesel engine with common-rail injection and variable valve timing. The result was an engine that emitted much lower levels of particulates and nitrogen oxides than normal. All of these technologies would become commonplace in the diesel engine of the future.

Peugeot 607 (2000)

When Peugeot introduced its 607 2.2 HDI in 2000 it sparked a revolution, as it was the first car to be sold with a diesel particulate filter (DPF) as standard. It would be another nine years before the technology became mandatory on all diesel-engined cars though.

VW invests in diesel (2000)

Having decided that diesel was the future, at the turn of the century Volkswagen planned a 10-strong range of oil-burning engines, topped by a 6.0-litre V12. We got the 5.0-litre V10 in the VWs Phaeton and Touareg, while Audi kept the V12 for itself.

Dieselmania hits (2001)

In May 2001 we reported on how sales of diesel cars had suddenly leapt in the UK, thanks to high-tech powerplants that produced cars that were better to drive than their petrol-engined equivalents. But diesels still accounted for just 20% of new-car sales.

Lotus Elise (2002)

In 2002 Lotus claimed that it was considering fitting an oil-burner to the Elise. We reported on the company’s plans just a fortnight before the opening of the Geneva motor show where the car was meant to make its debut. The car didn’t show, presumably because Lotus fans objected en masse.

Opel Eco Speedster (2002)

With just 1.3 litres in the middle, the Eco Speedster could crack 155mph and 113mpg. Autocar helped GM shatter a raft of performance and economy records in the summer of 2003, with the car averaging 141mph and 31mpg over 24 hours, beating the previous record by 61mph.

Skoda Fabia vRS (2003)

As recently as the mid-1990s, car magazines were filled with articles about how diesel engines could never replace petrol units, then along came Skoda with a hot version of its supermini – and it was offered only in oil-burning form.

Volkswagen Touareg V10 (2003)

When the wraps were taken off the original VW Touareg, buyers could opt for a monstrous 5.0-litre V10 diesel. It was seriously effective as VW proved; as a publicity stunt one was hooked up to a Boeing 747, which it successfully pulled.

Mercedes V12 (2004)

Diesel had really got into its stride by the early 2000s, with several car makers working on big oil-burning powerplants. There was talk of Jaguar developing a V12 diesel using Ford’s modular engine technology, while Mercedes worked on a 6.0-litre V12, which never emerged.

BMW 535d (2004)

BMW has long built some of the finest diesel engines available, and this was no exception. Take an already brilliant straight-six turbodiesel and bolt on a second turbocharger to create something seriously special, belting out 268 bhp and maximum torque of 413 lb ft, but promising 40mpg and a real-world one-tank range of over 600 miles.

Audi A8 3.0 TDI (2004)

At launch the second-generation A8 was offered with a fabulous 4.2 V8 TDI engine; a year later a 3.0 V6 TDI engine arrived. We could have chosen any number of cars that feature this fantastic engine, but the A8 makes best use of it with its high-tech aluminium bodyshell. Smooth, frugal and torquey, it was one of the best diesels on the market.

Honda Accord (2004)

Diesel engines were always rattly because their compression ratios were much higher than a petrol engine's. That was until Honda designed its first oil-burner, which was smoother thanks to its lower compression ratio. The car was good enough to claim 19 track-based world speed records along with a 92mpg average on a 419-mile road route.

Mercedes Bionic car (2005)

This was Mercedes’ vision of a diesel-powered future, which thankfully has not yet come to pass. Thankfully the tech was more encouraging than the design, as the direct-injection engine served up 118mph and 0-62 in eight seconds, but could still return 70mpg.

Audi R10 (2006)

A few years ago the idea of a diesel-powered car winning Le Mans would have been unthinkable, but the Audi R10 TDI notched up no fewer than three wins in a row, in 2006, 2007 and 2008. In 2009 the Peugeot 908 TDi won, then Audi racked up another two victories in 2010 and 2011 with the R15 TDI and R18 TDI respectively.

JCB Dieselmax (2006)

When JCB set out to break the diesel land speed record in 2006, it stood at 236mph – a record set in 1973. With a pair of 5-litre engines packing 750bhp between them, the record was obliterated, as JCB raised the bar all the way to 350mph.

Range Rover V8 (2006)

It wasn't the world's first diesel V8, but it was probably the one that was most overdue. Ever since the awful VM unit had been fitted years earlier, the world's best off-roader was crying out for a smooth, torquey V8; this was it.

Mercedes Diesotto (2007)

Mercedes engineers indulged in some tech overload when they developed the Diesotto prototype engine. This turbocharged 1.8-litre four-pot featured direct injection, variable compression and a hybridised starter motor – and could run on either petrol or diesel. A decade later Mazda announced that it would put an engine into production, capable of running on either fuel.

The death of diesel? (2007)

Sales of diesel cars had yet to peak in the UK, but in 2007 we were already reporting on the technology’s likely demise, reckoning that 2008 would be the peak. Rapid advances in petrol engine technology would make diesels redundant we claimed, but a decade on, real-world petrol-engine economy still can’t match that of diesel.

Audi Q7 V12 TDI (2008)

The antidote to the Smart and the only production car ever offered with a V12 diesel engine, Audi's Q7 V12 TDI was a complete and utter monster. Displacing six litres, there was 493bhp and 737lb ft of torque on tap, to give 0-62mph in 5.5 seconds.

Audi R8 TDI (2008)

Supercars are all about acceleration, which is provided by torque. So an R8 concept with a V12 diesel engine would be just what the doctor ordered – except Audi decided that the world wasn't ready for this oil-burning supercar.

Citroen Hypnos (2008)

The Hypnos offered the world a sneak preview of PSA’s new hybrid technology, dubbed HyMotion. With a diesel engine driving the front wheels and electric motors for the rears, this was four-wheel drive with a difference. We’d later see the tech in Peugeot’s 3008 and 508 Hybrid4 along with the Citroen DS5.

Ford Kuga (2008)

Reflecting buyers' habits, when Ford launched its Kuga small SUV it didn't even offer a petrol engine – it was a 2-litre diesel or nothing. Then for some inexplicable reason, along came a 2.5 petrol unit, which nobody bought.

Subaru Legacy (2008)

Subaru has long gone its own way when engineering cars; boxer engines and four-wheel drive are part and parcel of Subaru ownership. That didn't change when the company introduced its first diesel car, and the world’s first production flat-four diesel engine, back in 2008.

Volkswagen 1-litre concept (2009)

In the UK, a 1-litre car doesn't sound impressive, but in Germany it's something else altogether – it's a car that'll cover 100km on just a litre of fuel. That's almost 300mpg, and it's something this car can manage.

It was a statement of intent from Volkswagen; in 2007, it made the bold promise for its global car sales to hit 10 million-per-year at some point in the following decade, an increase from around six million-per-year at the time. Diesel would be central to this, as would conquering America, the latter with the help of the former. VW had long been an also-ran in the US, and leapfrogging Toyota and General Motors, where they were both strong, wouldn’t be possible without changing that.

Volkswagen EA189 engine (2009)

This is the brilliant engine that may well have killed diesel. Brilliant because, like its TDi forebear, this new four-cylinder common-rail powerplant delivered impressive power and torque figures along with excellent fuel economy. But Volkswagen penny-pinching ensured it was not equipped with the technology to counteract high levels of harmful emissions, notably Nitrogen Oxide. Instead, software in its Electronic Control Unit deliberately reduced harmful emissions only when the engine detected it was under emissions-test conditions.

Around 11 million of these engines with displacements of 1.2, 1.6 and 2.0 litres would be built. Developed with the US in mind, around 500,000 of the EA189 engines – only of 2-litres in size – would be sold in America, where they were fitted into the VWs Golf, Jetta, Beetle, and Audi A3. It was later estimated that the parts to make the engine compliant would have cost around US$500-per-engine.

Diesel in America

As part of its plan to succeed in North America, in early 2011 Volkswagen opened a new factory in Chattanooga, Tennessee, capable of producing 150,000 vehicles-per-year. Its first product was the Passat NMS for the 2012 model year. It was a slightly less sophisticated version of the Passat sold in Europe, and powered in diesel form by EA189.

The effort showed some success; from total VW US sales of 230,000 cars in 2007, sales rose to 400,000 in 2012, of which around a fifth were diesels. 'Clean Diesel' was marketed by VW as a green option as well as a performance one, with the torquey EA189 engine. Diesel promised similar fuel economy to gasoline-hybrids like the Toyota Prius but with much better driving characteristics and more responsive power, and because diesel generally emits less CO2-per-mile than gasoline, a helpful choice in the battle against climate change.

Mitsubishi ASX (2010)

Variable valve timing had been available for years on petrol engines, but until now, no diesel engine in a passenger car had ever featured it. The adoption of VVT on the ASX’s 1.8-litre engine improved efficiency greatly, to give performance with economy.

Peugeot 3008 Hybrid4 (2012)

Diesel cars cost more to build than their petrol equivalents, and so do hybrids. That's why diesel hybrids entered production years behind petrol/electric hybrids; they're too costly to make. That didn’t stop PSA from introducing the world’s first diesel/electric hybrid in 2012 – the 3008 Hybrid4.

Volvo V60 D6 (2012)

Just as PSA was launching its first diesel/electric hybrids, Volvo was blazing a trail by introducing the world to the concept of the plug-in diesel/electric hybrid. Rated at 48g/km and with a range of 621 miles, it could still acheve 0-62mph in just 6.2 seconds.

Volkswagen XL-1 (2013)

Having teased us with a prototype, Volkswagen then put its 1-litre car into production as the XL-1 – although only customers in Europe could buy one. Just 250 examples of the plug-in diesel/electric hybrid were built, and with a €111,000 (around $144,000 and £94,000) price tag you had to want one badly.

Volvo DRIVE-E (2013)

With diesel car sales booming, Volvo announced its revolutionary new DRIVE-E engine. This 2.0-litre four-cylinder powerplant replaced bigger units with more cylinders, but thanks to ground-breaking i-Art injection technology, economy, performance and refinement were all improved.

Dark clouds gather (2013)

In October 2013 we reported on how more stringent emissions regulations were going to hit diesel cars very hard; a year later the French government announced a big crackdown on diesels in a bid to clean up air in the country’s cities. This was just after London Mayor Boris Johnson had announced plans for an Ultra-Low Emissions Zone in the capital – targeting diesel engines in particular.

The investigation begins (2014)

Both West Virginia University’s Center for Alternative Fuels, Engines and Emissions  and the California Air Resources Board (CARB) had their suspicions generally that the diesels now joining American roads in large numbers were not as clean as advertised. They tested a VW Jetta diesel and a BMW X5 diesel.

Both performed as expected in lab test conditions; when they got out on the road in real-world conditions, the Jetta started emitting much higher amounts of Nitrogen Oxide (NOx) than permitted – by a factor of 15 to 35 times higher. The BMW’s emissions – equipped with a more sophisticated emissions-control system – were however in line with expectations and regulations.

Exposure (2014-15)

NOx is a key contributing factor to urban smog, and for geographical reasons the greater Los Angeles area is particularly prone to it (pictured), greatly exacerbated by very high car ownership, usage levels and congestion. So CARB takes a strong view on NOx.

The testers initially thought that some of their equipment was incorrectly calibrated, or that the car in particular had a specific fault. So they tested again, using different Volkswagens. However, a tester reported "... we did so much testing that we couldn't repeatedly be doing the same mistake again and again."

Reckoning (2015)

Volkswagen was alerted to the problem and obfuscated in response, blaming air pressure and test-route differentials. Finally, it responded that the high figures were caused by a technical error that could be resolved with a recall and software upgrade, which took place in early 2015. However, while emissions were reduced, the cheat device remained, and emissions were still above US legal limits.

CARB asked Volkswagen if the fix had brought emissions down to legal limits, but VW could not answer this, so CARB resolved to test a car – a 2012 Passat (an example is pictured) - that has been subject to the recall and thus the supposed fix. The high emissions remained. Some at CARB then became convinced that far from being a routine testing issue, something more sinister was afoot.

Disaster (2015)

After CARB repeated ever-louder questions to Volkswagen in the USA, in August 2015 a senior VW executive quietly confessed to the head of CARB’s testing lab that the diesel engine did indeed contain a defeat device installed to fool official emissions testing, explaining the high NOx figures seen, even after the recall fix. The US Environmental Protection Agency (EPA) was also informed. CARB was officially informed at the beginning of September, on the eve of the Frankfurt motor show, the biennial celebration of the German motor industry.

At VW’s traditional Group Night event, held the night before the show opened, the company’s various brands showed off their new models. VW CEO Martin Winterkorn gave a speech at the end (pictured) where he barely mentioned diesel and instead pledged to launch 20 new electric and hybrid cars by 2020.  That night he seemed less assured than usual; he was among the very few in the room who had any idea of the thunderstorm that was about to break out over the company.

Four days later, giving Volkswagen just half-an-hour’s notice, the US EPA held a press conference on September 18, accusing the company of using the illegal device used on 500,000 cars in America and millions more around the world. VW’s share price dropped 31% within a week and Winterkorn quickly departed, replaced by Porsche boss Matthias Müller.

The cost

The legal settlement agreed between VW and the US government saw VW agreeing to fix or buy back all the 500,000 offending vehicles, at a total estimated cost of $15 billion. A September 2016 study suggested that the vehicles in question emitted between 3,400 and 15,000 metric tons more NOx than they should have done. In January 2017, VW agreed to pay a fine of $4.3 billion to the US government in civil and criminal penalties, and several executives are being investigated and some face prosecution.

Volkswagen’s American offensive subsequently stalled, though not disastrously – sales of 366,000 cars in 2014 fell to 323,000 in 2016. But diesel, with its reputation utterly mauled, will no longer play any role in VW’s effort in America. And not for many others either – just 11 cars from five brands come with a diesel as of late 2017. 

The end?

The picture globally is little better; diesel vehicle sales are estimated to fall to just 4 percent of the global market in 2025, down from around 13.5% today. In the UK, diesel sales slumped 25% in January 2018 against a year previously.

Once seen as fuel for the future, it now seems clear that, given the increasing viability of alternatives, the fuel has no long-term future except, perhaps, as the power for very heavy trucks and other applications where high torque and reasonable fuel economy are vital. VW itself launched a new 7-seater SUV called the Atlas in 2017, built at Chattanooga; it’s not available with a diesel engine. In November 2016, VW announced it would no longer sell diesel models in the US. Volkswagen’s American diesel dream had come to an ignominious end.

Bentley Bentayga (2016)

In 2008 Volkswagen-owned Bentley stated categorically that its customers would never buy a diesel. Then it launched its first SUV almost a decade later and everything changed. It was unveiled at Winterkorn’s fateful final presentation in Frankfurt in 2015, just days before the storm over Volkswagen erupted. 

The diesel-powered Bentayga version features a triple-turbo 4.0-litre V8 rated at 429bhp and 664lb ft of torque. Despite officially being capable of 35.8mpg (or 29.8 miles-per-US-gallon), the SUV could crack 168mph along with 0-62mph in 4.8 seconds.

It may be something of a last hurrah for both Volkswagen diesels in particular and diesels in general.