With ubiquitous media coverage of vehicular air pollution and its links to public health, of car manufacturers' sometimes questionable practices plus announcements over dropping certain powertrains, and various cities across Europe and the UK increasingly introducing clean air and other zones or outright bans, diesel's days certainly appear numbered. Car leasing firm Vehicle Consulting investigates.

The environmental seesaw

Ironically, efforts by the government and other organisations to drive down harmful nitrogen oxide (NOx) and particulate matter by hiking the price of diesel and more heavily taxing its users have resulted in UK CO2 figures rising for the first time in fourteen years, as individuals and organisations switch to petrol.

Manufacturers' mixed messages

Car and parts producers seem split, with Peugeot ceasing diesel investment and Subaru axing the fuel entirely, while Bosch, Ford and Mercedes continue developing ever more efficient ‘black nozzle' engines and technology, the luxury German brand extoling diesel at the recent Paris Motor Show as still viable for mid-size and larger vehicles.

"Our customers' behaviour certainly supports the view that diesel is dead in the small car arena but is still very much alive for saloons, estates, MPVs and ever-popular SUVs, especially in the business sector", comments Craig Davy, commercial director at Vehicle Consulting, an established leasing and fleet management firm in Stockport.

Mazda is an exciting brand to watch, its latest SkyActiv-X petrol engines said to ‘combine the efficiency of diesel with the cleanliness of gasoline', while it has announced a focus on diesel-electric ‘mild hybrids' with 48V batteries and compact electric motors, filling the gap until its range is fully-electrified by 2030. Mild diesel-electric hybrid technology is also being championed by Audi and many other marques, often resulting in genuinely impressive fuel consumption figures and CO2 values, as important as ever for business drivers.

WLTP and other tests

September 2018 saw the new WLTP test introduced, bringing greater realism to cars' MPG and CO2 figures at a time when various investigations are uncovering scandalous results, with Which? magazine, for example, testing 46 cars to find that they all emit, on average, nearly four times the NOx permissible under the latest Euro 6 rules. Renault fared badly and Mercedes came out very favourably, while in CO2 tests, many popular small cars performed poorly, including the hybrid Kia Niro with disappointing MPG and over three times the cited CO2.

Hybrids are improving fast

Hybrids have traditionally performed less well on motorways compared to diesels, but although the latest batch of tests unsurprisingly see diesels from the likes of Mazda and Mercedes top the charts, Toyota's Prius in conventional, self-charging rather than plug-in hybrid guise performs strongly around 70mph as well as around town, long hybrids' domain. The new Hyundai Ioniq hybrid is also carving a good name for itself in terms of across-the-board fuel economy in real-world situations.

"Many leasing and finance customers from both the private and business segments still have a preference for models perceived as premium, though", comments Craig Davy. He adds: "Although three-digit MPG figures are a misnomer when it comes to hybrids, the Volkswagen Golf GTE is an attractive all-rounder with achievable economy around 70mpg and annual running costs under £300."

A different driving style is required to eke the most out of a hybrid, not accelerating away from junctions slowly, which ordinarily encourages healthier MPG figures, but instead being firmer with the throttle, reaching the target speed more briskly then taking one's foot off the accelerator to allow regenerative braking to recharge the battery.

Plug-In Car Grant disappointment

The government recently announced that category 2 and 3 vehicles will no longer be eligible for the grant, which means that plug-in hybrid cars, once promoted as the way forward, will be more expensive to buy, or cost around £65 per month more to lease on a 3-year contract.

Between now and 2020, only eligible fully-electric vehicles that can travel at least 70 miles without emitting any CO2 will receive the reduced level of £3,500 support. Although it's understandable that the government wants full EVs adopted sooner rather than later, this move is somewhat disappointing even if it was inevitable.

"Many manufacturers are set to introduce self-charging and plug-in hybrids throughout 2019, so it's conceivable that some will find ways to lessen the effect of the PICG changes. Hybrids are a great choice for many drivers who aren't in a position to accommodate the lengthy recharging times, patchy charge point availability and generally higher prices associated with fully-electric cars", comments Craig Davy.

All things considered

Congestion zones are increasingly being mooted for many UK cities and towns, but viewed realistically, Oxford doesn't look likely to ban all non-zero-emissions vehicles until 2035, and London's T-Charge doesn't apply to the latest Euro 6 engines, which most new vehicles incorporate.

Diesel is still usually the best fuel for drivers who tow caravans or trailers, and for those who cover around 20,000 or more miles each year, while petrol is ideally avoided for larger SUVs and saloon cars. For most other motorists, though, hybrid cars are shaping up to be the most attractive prospect on the whole, presenting a good case for bypassing petrol entirely. While plug-in iterations require more discipline when it comes to charging, conventional self-charging hybrids are improving all the time and the desired sustained uptake in demand will hopefully translate to prices lowering further.

Reading impartial road-test reviews and visiting owners' club forums to obtain real-world findings are worthy steps to ensure that the right car and right fuel are chosen for each circumstance.

Only history will determine what will happen if car CO2 emissions continue rising after years of hard work reducing them, but the new WLTP emissions test and rising diesel pump prices combined with national and local policies and public sentiment won't slow diesel's imminent demise - making now the ideal time to take the plunge and embrace hybrid power.