Recent years have witnessed a paradigm shift from diesel to petrol with several carmakers operating in India withdrawing diesel powertrains from their line-up. The likes of Renault, Honda, Volkswagen, Skoda and Maruti Suzuki have halted retail of their diesel engines. For many, the Government’s 2020 implementation of BS-VI emission norms served as the trigger, while some even cite the rising diesel prices as a contributing factor. And there are those who see the development and forthcoming transition to hybrids, battery-operated or hydrogen-powered cars as crucial reasons for the dirtier diesel engines getting neglected.

‘Kitna deti hai?’ A catchphrase most Indians live by and associate Maruti Suzuki with. India’s largest carmaker, Maruti Suzuki, has been synonymous with offering fuel-efficient cars at affordable prices to the Indian masses. As it caters to the Indian penchant for acquiring value-for-money products, one in every three cars in India is a Maruti Suzuki.
 
With the Indo-Japanese brand preferred by the majority, the next car-buying decision is to choose between petrol and diesel options. Indians are famed to opt for the most fuel-efficient option, which puts diesel powertrains at the forefront. About a decade ago, diesel engines constituted about 60 percent of total passenger vehicle sales in India. However, the share of diesel cars in the present day accounts for only 17 percent. 

Before forming any further assumptions, let us explore the possible factors that might have contributed to the same.

BSVI Emission Norms
The emissions produced in most internal combustion engines comprise numerous harmful gases such as carbon dioxide (CO2), carbon monoxide (CO), hydrocarbons (HC) and oxides of nitrogen (NOx) and particulate matter (PM). As diesel is the dirtier fuel among the two, the BS-VI emission norms are much stricter with diesel than they are with petrol.

While petrol’s upgrades get limited to catalysts and electronic control upgrades, diesel upgrades comprise many more elements, entailing higher costs and the need for extensive development time. Moreover, petrol engines need to carry a mere 25 percent reduction in NOx emissions to make the engine compliant. But with BS-VI diesel mills, car companies have to reduce the same pollutant and PM emissions by a whopping 68 percent and 82 percent, respectively.
 
The authorities even mandated three equipments to ensure the pollution levels were kept in check with the new guidelines. This pool constitutes a DPF (Diesel Particulate Filter), a SCR (Selective Catalytic Reduction) system, and a LNT (Lean NOx trap). The DPF reduces the emission of PM into the atmosphere, whereas the SCR and LNT come in handy in trapping the excessive NOx emissions, a byproduct specific to diesel engines.
 
Tweaking the DPF is said to be a particularly troublesome task as Indian conditions aren’t the most ideal for it. Running a diesel engine comes with the risk of soot, an excessive fuel build-up caused by incomplete fuel combustion that ultimately gets deposited in the DPF tank. DPF requires the car to be running at higher speeds to achieve temperatures of around 600 degrees celsius to burn the excessive soot within. However, the lower average speed of cars in India implies carmakers can manage only 400 degrees celsius in the DPF, making it unviable. Many auto companies consider injecting diesel a compliant tweak, but any excess injection can cause a fire underneath. To validate such components, extensive testing of over six to seven lakh kilometres needs to be conducted, which can increase the entire development cycle!

Our Government decided to skip an emission stage to keep our country’s pollution norms in pace with other developed Countrise. Had the Government not executed the leapfrogging, the ideal situation would have seen authorities launch emission equipment in an orderly fashion with BS-V norms welcoming the introduction of DPF and the SCR device reserved for a stage VI launch. This would have provided carmakers with the required time to earmark costs, separately assess each component and synergise everything at the end.

Instead, the BS-VI norms mandated all components along with the LNT device to be installed in one go. Automakers claim both DPF and SCR devices getting tested together are futile as identifying and determining the faulty device between two, in case of an error, is extremely difficult. Add the three to four-year timeline required for testing and optimising these pollution-preventing devices to work in Indian conditions to the mix, and you’re looking at an exercise that could get rendered unusable with the impending electrification.

BS-VI Upgrade Impacts Performance
There is a myth regarding BS-VI engines being more potent than their BS-IV counterparts because of cleaner combustion and advanced pollution-trapping technology deployed. However, this installation of advanced technological devices adversely affects the engine’s performance, resulting in a loss of power.
 
Cleaner engines generally entail a slow combustion process. A good example of that being reduced sulphur content in diesel translates to a reduction in its energy density, ultimately affecting the combustion process. Plus, multiple exhaust filters such as DPF and SCR working together dampen the flow of exhaust gases as well. To simplify further, automakers deliberately restrict the BS-VI engine’s breathing procedure (intake and exhale of air and gases) to trap the polluting elements and comply with the stringent emission norms. However, this takes a toll on the vehicle’s performance and fuel efficiency, resulting in the BS-VI powertrains being more likely to be less powerful than its earlier iteration.

BS-VI Diesel Upgrade Came At A Higher Premium
India has established its reputation as a highly price-sensitive market. Hence, any upgrades required to meet BS-VI emission norms had to see minimised production costs, which the consumer would ultimately bear. Upgrades to petrol engines were relatively easy and cheaper to execute, but the story with diesel engines was a comprehensively expensive affair with the mandated installation of multiple exhaust systems that diminished its business viability.
 
Before the implementation of BS-VI emissions norms, the average price difference between petrol and diesel power plants was around one lakh rupees. But post the implementation of the emissions norms, Shashank Srivastava, Executive Director, Sales and Marketing at Maruti Suzuki India Limited, believes ownership of diesel cars does not make much economic sense. ‘In the BS-VI regime, the acquisition cost of diesel car is higher by anywhere between Rs 1.25 lakh and Rs 2.05 lakh over the petrol variant and if the running cost of diesel car is not lower (as it was before), it doesn’t make economic sense to buy a diesel car’.
  
Furthermore, the rising diesel prices means recovering the upfront premium paid during the acquisition would take much longer. In the earlier scheme of things and a price difference of Rs 25, the higher retail price and the associated maintenance costs could be retrieved in around five years, provided the car was driven for a minimum of a 1,000 kilometres every month. But now, that difference is down to Rs 10 - 15, which would extend the time taken to recover the initial premium paid for the diesel engine, increasing the feasibility of petrol engines. With the majority of Indians not having a monthly running average of 1,000 kilometres, investing in petrol engines makes more business sense: not to forget the idea of burning the cleaner fuel out of the two serving as an added advantage.

Negative International Sentiment Towards Diesel
In 2015, Volkswagen (VW) rocked the global auto industry when it admitted to having emissions-cheating devices installed in its vehicles. Further investigation by the US Environmental Protection Agency (EPA) revealed that over 5,90,000 diesel motor vehicles had defeat devices installed to cheat through federal emissions tests whilst generating emissions 40 times more than the permissible limit during daily operation. This resulted in VW getting charged fines amounting to USD 33 billion and forever registering a dent in the German carmaker’s image.

Prior to this, multiple carmakers were lobbying with the governments to promote diesel and make the general public believe that it was better for the environment. Scientific evidence stating diesel fumes might cause cancer cut short these pleas and the VW dieselgate scandal was the final nail in the coffin for the diesel decline to commence.
 
Even before the emissions norms hit the carmakers in India, the global sentiment towards diesel had already turned negative. In 2017, diesel sales in the UK plunged by a whopping 17 percent, whereas France reported a diesel sales drop of under 50 percent, a first in 17 years. With the global demand for diesel witnessing a massive downfall, auto companies couldn’t see the feasibility of upgrading all existing diesel powerplants to the latest emission norms to suit the shrinking target market. Hence, one can find diesel engine options are restricted only to the larger heavy-duty segment of automobiles such as SUVs and pickup trucks.

Carmakers Taking A Stand On Diesel
In 2012, diesel accounted for 60 percent of all passenger vehicle (PV) sales, influencing carmakers to invest heavily in diesel powertrains. In the current circumstances, petrol constitute as high as 82 percent in PV sales. Diesels make up for a paltry 16 percent, with the remaining two per cent being shared by CNG and electric-powered cars. These numbers are strong enough to denote a solid movement towards petrol paradise until the transition to any other resource is made.
 
Shashank Srivastava, Executive Director, Marketing & Sales, Maruti Suzuki India, says, ‘In the April-October 2020 period, less than 0.3% diesel cars were sold in the overall hatchback segment. In hatchbacks and sedans together, the diesel engine sales share is less than 2%, and in the MPV segment it is 22%. It’s only in the SUV space that diesel engine cars still enjoy a substantial share, but even within that, in entry-level SUVs, the share is just 30%”.

And as the saying goes, a curse to one is a boon to another. In this case, Maruti Suzuki’s decision to halt all diesel engines from retail has allowed Tata Motors to swoop in and enjoy that recently-vacated market share with its range of BS-VI compliant diesel crossovers and SUVs, a predominant Tata forte. Another Indian carmaker, Mahindra and Mahindra, decided to bring its diesel powertrains within BS-VI emission norms as most of its offerings such as the Thar, Scorpio and   XUV700 fall under the SUV category, complementing the same. 

India’s second-largest carmaker, Hyundai, will also be reverting to petrol once its current line-up of BS-VI compliant diesel engines is exhausted. The South Korean company chalked a route where consumers would eventually bear the entire expenses but in phases to offset the additional developmental costs for limiting the emissions. But the overall pickings for diesel have reduced drastically. If one out of every two cars sold in the country was a diesel previously, the current situation flips that stat to one out of five.

Is It Game Over For Diesel?
The time for diesel is running out fast. The shrinking price difference compared to petrol, the higher maintenance costs, even larger retail price, stringent emission norms and the mindset of not driving a polluting car come together to sway an average Indian car buyer away from diesel. More importantly, one can infer that the demise of diesel seems inevitable when considering specific body styles such as hatchback and sedans.
 
It should be noted that the SUV segment has been on the rise for the last couple of years. Only the SUV segment enjoys a significant slice of the diesel pie. The mighty torque-friendly nature of diesel engines supports the rugged looks and persona of an SUV, making them a great match. Hence, it won’t be accurate to expect a complete shift in petrol engines, especially for utilitarian larger crossovers and SUVs.
 
Diesels could elbow their way in the cleaner, environment-conscious world but find a home only within long-hauling vehicles, most probably constituting the transportation and logistics sectors. Though, the daily advancements in battery energy capacity, expanding charging network and the ever-strict emission norms will put a certain stop to diesel operations entirely soon.

Emission Laws: The Background
In the 2000s, the Indian Government introduced the Bharat Stage Emission Standards (or the BS Stage) to regulate the pollution output generated by combustion-engined vehicles. It was based on the European emission norms, and all carmakers had to comply with the set criteria to retail products within the subcontinent.
 
The first three BS stages were announced within a decade. Every subsequent BS level imposed more stringent emission norms to curb pollution from the exhaust system. However, BS-IV or Bharat Stage 4 didn’t see an implication until 2017, a massive seven year delay since the 2010 enforcement of BS-III.
 
This should have further cascaded into a series of delays in imposing stricter emission laws, but the Government declared its idea of skipping the BS-V stage entirely. This allowed the ministry to introduce the BS-VI emission norms as early as 2020, bringing India’s emission norms at par with that of the USA, Europe and other developed countries. Though this also meant carmakers were forced to develop BS-VI compliant engines to continue retail promptly.
 
While this aids in extending our little blue planet’s life, courtesy of less polluted air, it must have increased the resource expense for carmakers. Not only did this force auto companies to invest capital and time that otherwise would have been diverted to the upcoming EV transition, it also made them question the long-term feasibility of the BS-VI upgrade. With European countries pledging to ban the sale of petrol and diesel cars as early as 2030, the electric future is inevitable. Hence, the shift from BS-IV to BS-VI would not have made business sense for diesel as the sticker price would end up being higher than petrol, and the reducing price difference between the two would not help its case any further.