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Diesel’s day is here. Or at least, it should be, given how far modern diesel-powered cars have come. The Highway investigates…
FORGET THE SMOKY, clattering diesel engines you encounter in taxis and lorries. The woeful clamour and sooty flatulence they emit are completely unnecessary in today’s world, for the fact is that a modern, well-tuned diesel engine is neither noisy nor dirty. So far it’s mostly Western Europeans who have caught on to the fact. In their part of the world, diesel power now accounts for roughly half of all new cars sold, and in markets like Austria and Belgium, almost two out of three new cars is powered by diesel
The rise of diesel power has been nothing short of spectacular. The latest diesels have made huge strides in refinement, cleanliness and efficiency again, with current technology capitalising on the diesel motor’s frugality to eke out amazing fuel economy.
What makes a diesel so frugal? First, the engines work completely differently from petrol engines. While a petrol motor ignites fuel with an electric spark, a diesel engine fires up on compression ignition.
Gases get hotter as you compress them, and a diesel engine can run compression ratios as high as 25 to 1 (roughly double that of petrol engines) to get the air in its cylinders as hot as 900 degrees Celsius. The diesel is injected into the hot air, which is what ignites it. Glow plugs (metal filaments which heat up when electricity is applied through them) are sometimes used to warm up the engine for cold starts, but these are rarely used beyond the first few seconds of a diesel engine’s operation.
The high compression ratios contribute to the engine’s efficiency and adding a turbocharger to compress the air before it enters the cylinders only makes things better.
Another factor that makes diesel-burners so frugal is that the fuel itself is denser than petrol. Although a kilogramme of petrol and diesel contain almost the same number of calories (a measurement of energy), fuel is sold by the litre. And since diesel is denser than petrol by about 15 percent, you actually get more energy per litre of the stuff. That, coupled with the higher efficiency of the diesel engine, is a large part of why you can get up to much further with a diesel engine than you can with a similarly powerful petrol motor.
An automatic BMW 325i that runs on petrol, for example, sprints to 100km/h in 7.7 seconds, while a diesel-powered 330d smokes it at 6.8 seconds. And yet the diesel- burner uses some 20 percent less fuel!
Naturally, because carbon dioxide emissions are directly proportionate to the amount of fuel burnt, the diesel churns out less of the greenhouse gas, too: 197 grammes per kilometer, versus 218 grammes for its petrol counterpart.
But what about black smoke? The latest, Euro 4 standards compliant diesels have particulate filters that comb the stuff from exhaust gases. Engine computing and fuel injector technology have also improved to the point that diesels control their fuelling so well that they can run as clean as many petrol or CNG variants.
Diesels have even begun to flex their muscles on the racetrack. Audi created history this year by becoming the first manufacturer to win with diesel power at the 24 hours of Le Mans race, the most prestigious and challenging endurance race in motorsports. Running on regular Shell diesel, the 650bhp Audi R10 followed up its Le Mans win with a victory at another endurance race in the US three months later. So much for diesels being slow then…
But perhaps the most telling sign of the diesel engine’s rise to prominence came at the 2003 Paris motor show where Mercedes-Benz had brought along what were then concept versions of the B-Class and R-Class MPVs. But what caught the eye was the fact that, apart from the pair of prototypes, not a single petrol-powered car was to be found at the Mercedes stand.
Arguably the most forward-thinking car maker in the world had turned up at an A-list international motor show with an all-diesel line-up. Which should tell you something, really.
Citroen’s super-clean Berlingo van gives us an idea of just how far diesel technology has come – and precisely what many drivers are deprived of in Singapore.
While you wouldn’t currently drive a diesel saloon locally due to prohibitively high import taxes, you can enjoy the latest Euro 4 diesel emissions technology if you run a company and choose to buy a commercial vehicle.
The Highway took the latest Citroen Berlingo 1.6 HDI Turbo diesel van for a spin to see how its oil-burner stacks up to similar sized four cylinder petrol engines.
Fire-up the Berlingo and after an initial couple of seconds of a muted and deep-throated rattle that all diesels are synonymous with, the idle speed settles down to an almost silent hum. If you didn’t know better, you might think with was petrol-powered. Open up the throttle at road speeds and it’s a similar story, although at higher rpm and once road speeds exceed 70kmh there’s a distinct difference in the aural feedback. Now it certainly doesn’t sound like a petrol engine anymore – but it certainly doesn’t sound like a diesel of yesteryear either. It has a refined note, with a hushed background rumble that just starts to feed its way through the cabin.
From the word go though it still performs like a diesel through and through. And that’s a very good thing. What diesels are blessed with are bagfuls on instant torque. The Berlingo’s peak torque of 175Nm is reached at only 1,750rpm. With most petrol engines you are still struggling to get into the power band at that engine speed. It made strong, safe overtaking in the Berlingo a cinch without having to fight with the five speed manual gearbox. In fact, so flexible is the torque curve on this 75bhp unit that it can pull away in third gear from nearly standstill without the drive-train stuttering and feeling like everything is going to stall with a sickening crunch. If you are lazy, just leave it in third half the time and drive it like an auto.
One thing that diesel engines are even more accomplished at than great pulling power is the ability to return astonishing fuel returns. After filling the Berlingo’s tank to the brim with Shell’s Ultra Low Sulphur Diesel and running it around Singapore’s expressways and CBD areas for a total of 163 kilometres, it took just 7.2 litres of fuel to top it up again. That equates to just 4.4 l/100km. Granted, the van wasn’t loaded at the back, but it is also fair to say we were deliberately heavy on the accelerator pedal too. It would clearly have made even better returns without the stop-start driving of the inner city areas.
Shell spoke to the Highway about its investment in ‘cleaning up’ existing diesel fuels and how sulphur – an element found naturally in crude oil – is one of the major contributors to acid rain after diesel fuel is combusted. The use of Ultra Low Sulphur Diesel (ULSD) was mandated in Singapore on December 1 2005 and Shell was the first company to introduce it here in June 2005 to enable Euro 4 engines to meet the new standards. This Shell fuel has reduced sulphur content from the previously high levels of around 0.5% (or 500 parts per million) to around 0.05% (or 50 parts per million). However, that’s not the end of the story, as the latest Euro 4 emissions particulate filters, which soak up the sulphur from engine emissions, need a low level of 0.05% to operate efficiently. Simply reducing sulphur from 0.5% to 0.05% would have little effect on air quality itself without the associated vehicle technologies like these diesel particulate filters. Bio-fuels also have a future to play with diesel. Shell, the largest user of bio-fuels worldwide is currently looking at producing clean diesel from natural gas (Gas to Liquids), Bio mass (BTL) and coal (CTL). This is likely to be the next generation of cleaner than ever diesel fuel.
Aggie Krasnolucka
is Programmes Director at the FIA Foundation where she looks after its portfolio of road safety interventions as well as leads the Motorcycle Initiative – a global hub of interventions working towards improving motorcycle safety across areas of helmet safety, infrastructure, technology, and legislation.
Previously, she worked across different areas of the international development context including community outreach and engagement, road safety, access to health, private public partnerships as well as fundraising and communications. Aggie holds a master’s degree in social anthropology as well as linguistics and literature.
Professor Wong
is currently a Full Professor at the Department of Mechanical & Manufacturing Engineering, University Putra Malaysia. He has been serving the department and the University since 1997. During his service, Professor Wong was seconded to Malaysian Institute of Road Safety Research (MIROS), a Statutory Body in Malaysia (with MIROS Act 2012) and a national research institute in Malaysia in December 2007 as the Director of Vehicle Safety and Biomechanics Research Centre. He was then appointed as the Director-General of MIROS in August 2011. His 10-year secondment to MIROS ended in September 2017 and was appointed to be the MIROS Board Director. In February 2022, Professor Wong is appointed as the Chairman of MIROS Board of Directors. Professor Wong is also appointed as an Adjunct Professor of Qatar University. He served as the Special Advisor on Road Safety to the Minister of Transport and Communications Myanmar till 2021. He was appointed to serve in the Steering Committee of the United Nations Road Safety Fund from 2022 to 2024. Recently Professor Wong was appointed as the Fellow of the Academy of Science Malaysia.
Professor Wong has driven the drafting, deliberation and enactment of MIROS Act 2012 by the Parliament of Malaysia. He is also directly and indirectly involved in establishing numerous national and international initiatives and interventions in Road Safety, amongst them are rear seatbelt law, national implementation framework of UN WP29 Regulations, enforcing various UN Regulations on Road Vehicles, airbag fitment, ASEAN New Car Assessment Programme (NCAP), International Road Assessment Programme (iRAP) for Malaysia, Guideline for Road Safety Audit, Code of Practices for Transport Sector under OSHA Malaysia, ISO39001 road traffic safety management systems and the competence requirements for auditing and certification in ISO17021-7, Pilot implementation of ISO39001 in Malaysia, use of electric cars, motorcycles and bicycles, in-depth crash and accident database, Automated Enforcement System, Mandatory of Electronic Stability Control System, Revision of Drive Under Influence, Malaysian Accident Emergency Call Systems Initiative, Endorsement of 2015 ASEAN Declaration on Road Safety Strategy by ASEAN Transport Ministers, road safety recommendations to the Government of Myanmar with in-Country Expert Mission to Myanmar, and many others.
Mr. Michihiro Toki
is a seasoned mobility and road safety expert with over 25 years at the Japan Automobile Federation (JAF). He currently serves as Manager of the Project Development Division in JAF’s Traffic Environment Department, leading national road safety campaigns and sustainable mobility initiatives.
Mr. Toki began his career in 1998 as a roadside assistance patrol officer, gaining hands-on experience with the diverse challenges faced by drivers in Japan. He transitioned to membership promotion in 2006, working with automotive dealers to expand JAF’s member base.
In 2018, he assumed a leadership role at the branch level, overseeing road safety, motorsports, and public relations. As a JAF Certified Safety Advisor, he delivered safety lectures, managed motorsport activities, and led public outreach. Promoted in 2021 to Section Manager, he expanded his role to include Safety Advisor training, PR strategy, and membership benefit development.
Appointed to his current position in 2024, Mr. Toki now directs the training of Safety Advisors nationwide and develops interactive programs for diverse audiences, including international drivers. He collaborates with government and industry partners to tackle traffic safety issues.
Beyond JAF, Mr. Toki serves on national bodies including the Sub Study Group for Advanced Safety Vehicles (MLIT), the Cabinet Office’s Traffic Safety Forum, and as Vice-Chairman of the Training Commission at the Japan Automobile Education Foundation.
Mr. Toki is recognised for his dedication to public safety, his strategic leadership in mobility initiatives, and his deep commitment to enhancing the driving culture in Japan.