Diesel vs Petrol vs Electric: A realistic fleet perspective on the ongoing fuel debate

Driving Awareness

Diesel still remains a firm favourite for business fleets; and we believe it should. New Euro 6 diesel engines are some of the cleanest on the market and can measure up to their petrol equivalents in terms of pollutants.

The table below shows Euro 6 emissions standards for both diesel and petrol cars, indicating just a 0.020 mg/km difference in Nitrogen oxides (NOx):

 Carbon monoxide (CO) Nitrogen oxides (NOx)Particulate Matter (PM)

Over the past few years, diesel cars have been demonised by the Government and in the press, and as a result of such propaganda, diesel’s credibility has been severely damaged.

Of course it’s not all roses for diesel. Over the years, diesel cars have undoubtably contributed to the high level of nitrogen dioxide concentrations in the UK, but the emphasis should be placed on older diesels. Prior to 2000, there was no limit for NOx emissions regarding Euro emission standards, so these older diesels still on UK roads today could be emitting any number of harmful gases. But what needs to put into perspective is that from 2000 to 2016, the NOx emission standard threshold has been reduced from 0.15g/km to 0.060 g/km. That’s a huge reduction of 84%!

So far, all the recent bad press and noise has achieved is scaremongering the everyday driver into thinking diesels are dirty. And this has without a doubt spilled over to company drivers.

Despite company car tax banding still favouring diesels regarding CO2 emissions, company car drivers are now taking a closer look at alternatives to diesel, namely Plug-in Hybrid Electric Vehicles (PHEVs) and electric vehicles.

PHEVs & electric vehicles: The lure vs the reality

Hybrids and electric vehicles are without a doubt the future of cleaner motoring. But are we trying to run before we can walk?

For company car drivers, Plug-in Hybrid Electric Vehicles (PHEVs) are particularly attractive. Not only do as they offer low CO2 figures that benefit their BIK tax, but they present no charge or range anxiety thanks to the trusty combustible engine onboard to back drivers up when the electric juice runs out.

However, with more to them than meets the eye, we look some of the top ways PHEVs and electric vehicles may still be unsuitable for fleets and high-mileage drivers:

  • Fuel costs

For the average company car driver, annual mileage is 30,000+. It has been these high mileage drivers that have flocked to diesels in the past as they offer the much better efficiency compared to that of a petrol. Suddenly you throw a PHEV in the mix and diesel doesn’t look so strong…

As an example, we compared the BMW 5 Series saloon across the full range:


BMW 530e SE 4dr Auto
BMW 530e

BMW 525d SE 4dr Auto
BMW 525d

BMW 530i SE 4dr Auto
BMW 530i

Combined MPG141.257.651.3
Monthly Fuel Costs £29.68£73.99£81.69

From these figures alone, it looks like a no brainer. But how can the running costs be so strong on the PHEV?

That’s because they are based on its electric capabilities. These levels can only be achieved when you can keep the car in it’s most efficient electric mode, which goes straight out the window should you do more than 20 miles in one trip or exceed 30mph. Therefore, not all suitable for a company car driver doing 100+ miles a day up and down the motorway.

For high-mileage company car drivers who aren’t going to get the best use from the electric engine, it would be more accurate to simply compare diesel and petrol.

Just this month, mileage and expenses management specialist, TMC released real-world fuel consumption analysis of 7,000 fleet cars.

The results showed that the real cost gap between diesel and petrol is much wider than many people realise and on average, diesels were 38% more efficient than petrol equivalents.¹

  • Servicing

Another cost implication to consider is that PHEVs are subject to servicing every 10,000 miles or every 12 months. As you can appreciate in PHEVs, as you switch between the electric and petrol mode, the motors are constantly activating and deactivating. Under these types of operating conditions, the engine oil will deteriorate more rapidly and will require frequent oil changes.

Not only does this mean you’ll be paying twice as many services as opposed to that of a diesel equivalent, but vehicle downtime will be much higher when the vehicle is in the garage being serviced. Vehicle downtime can be much more costly for a business.

  • Availability

As PHEVs grow in popularity, availability becomes tighter. Plug-in hybrid sales are on the increase year on year, with sales going up by 40% from Jan/Feb 2017 to Jan/Feb 2018.

Waiting times are also ever increasing with some manufacturers closing the order book completely on popular models such as the Volkswagen Golf GTE, BMW 330e and Mercedes-Benz 350e.

  • Charging infrastructure

To get the most out of your plug-in hybrid (and to have even a hope at hitting some of the performance figures manufacturers suggest) regular charging is a must.

A recent report released by PWC in April 2018, Charging ahead! The need to upscale UK electric vehicle charging infrastructure ², indicates that people who currently charge their vehicle at home do so during a three-hour window at the end of the day between 5-8pm. According to PWC, “assuming that habits continue, then we will need more residential grid reinforcement to cope, or alternative solutions to smooth peak demand.”

Not only are the UK residential power grids not ready for a substantial rise in people charging their cars at home but also the public charging infrastructure is severely lacking too. In the same report, PWC shows the rate of electric vehicles growing at a rate of 98%, the UK’s public charging infrastructure is growing much slower at just 44%.

Without adequate charging infrastructure in place, company car drivers will not be encouraged to plug in their car which is the way to get the best efficiency from their car.

In conclusion, inadequate charging means that these lower-emission vehicles will be performing far worse than the diesel alternatives people have been warned away from.

¹ Source: themilesconsultancy.com, ² Source: pwc.co.uk

For more advice and support on what options are suitable for your fleet, contact us on:

0115 946 6466

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