12th October 2016

Should fleets switch from diesel to petrol as promptly as possible?

Last month, the City of London Corporation announced that when vehicles from its 300-strong fleet become due for replacement, diesel models will no longer be considered except in the case of specialist vehicles for which no alternative fuel type is available1. With Camden Council already having introduced its own cessation of the purchasing and leasing of diesel vehicles2 earlier in 2016 and new London Mayor Sadiq Khan looking likely to launch the ‘T-Charge’ penalising dirtier diesels entering the capital’s heart3, the UK clearly doesn’t want to lag behind in efforts to reduce vehicular air pollution.

Across the Channel, Paris has now banned pre-1997 vehicles from its streets during weekday working hours4 and its mayor has expressed the desire to make the city diesel-free by 2020, a mere few years away. Europe’s automotive and economic powerhouse, Germany, is also poised to accelerate the clean-up of its cities by allowing access only to vehicles meeting the latest Euro 6 standards5.

Such countries are scrambling to reduce nitrogen oxide (NOx) and particulate matter (PM) emissions as their societies become increasingly aware of these dangers, a study by King’s College London finding that almost 9,500 people die annually in the capital6, particularly from prolonged exposure to nitrogen dioxide (NO2) and fine particles called PM2.5 – which are both significantly blamed on diesel vehicles.

Whilst some fleets and their managers are proud to be early adopters, pursuing any automotive technology advancements, it’s inevitable that a proportion choose to keep their focus on the short-term, damage to the environment and the long-term impact of diesel vehicles not as important to them as more immediate economic efficiencies.  Fleet managers with short-sighted aims may ultimately be swayed by resale values, though, if it becomes apparent that auction buyers are no longer interested in snapping up ex-fleet diesel cars that have come to the end of their leases.

Diesel cars have long been more expensive to purchase, fuel and service than their petrol counterparts. It might therefore seem that the obvious solution in the short term, until pure EVs and PHEVs become more affordable, is for business fleets and private motorists to revert to petrol power. After all, the latest 3-cylinder petrol engines are proving to be efficient, low on emissions and able to deliver ample performance. It’s not quite that simple, though.

By their very nature, even the most impressive petrol engines out there aren’t able to turn more than around a third of the energy contained in the fuel into propulsion power, whereas modern diesel engines can typically achieve a conversion of roughly half. What’s more, petrol vehicles still contribute to CO2 greenhouse gases, effectively trading one form of air pollution for another.

The answer for some fleets may lie in a drivetrain called the ‘mild hybrid’. Such a system combines a small, conventional petrol engine and a traditional automatic gearbox – as opposed to the more complex types found in full hybrids – with very basic electrical assistance. The engine, often a low-displacement unit, perhaps even of 3 cylinders, is given a boost by stored-up energy being released from the modest on-board battery.

VW’s 8th generation Golf is set to offer a 48V mild hybrid option7 in conjunction with Bosch, and the next Audi A88 and Mercedes S-Class9 are also in line to receive mild hybrid powertrains, but fleets utilising more compact cars are also catered for by the likes of the excellent new Suzuki Baleno SHVS (Smart Hybrid Vehicle by Suzuki). The hatchback uses an Integrated Starter Generator (ISG) to assist the engine when it accelerates and, as is typical with mild hybrids, regenerative braking technology is also part of the action and proves more efficient than a bog-standard alternator.

Driver behaviour also has a bearing on whether a fleet should revert back to purchasing or leasing petrol vehicles instead of diesel, as a car’s efficiency certainly won’t be achieved through aggressive or generally profligate driving. Smoothness and anticipation substantially contribute to how economical a vehicle will prove to be; which is one of the ways in which purely app-based telematics systems like Appy Fleet can work wonders for fleet managers.

Larger fleets will unarguably continue to run a mixture of differently-fuelled vehicles for the foreseeable future, heavy commercial or specialist vehicles still reliant on diesel, along with some rep-mobiles notching up stellar annual mileages – but many fleets will soon start investigating mild hybrid technology. Combined with efficient driving, which also keeps employees safer, this technology could nicely hold the fort until electric and indeed autonomous vehicles become affordable for fleets and other punters.