Engines vs batteries

  • Decide which powertrain suits you best
  • Pros and cons of each revealed
  • Is now the time to switch to battery power?

If you missed the Volkswagen emissions scandal you must have been living under a rock for the past few months. 

The story made front pages in September 2015 when the Environmental Protection Agency (EPA) found that many of the firm's cars in America had a "defeat device" fitted to diesel engines, which could detect when they were being tested, and change the overall exhaust emissions.

At first it was thought that it only affected cars in the US but in November, Volkswagen also admitted finding irregularities in tests to measure CO2 emissions which could affect cars in Europe.

Aside from the financial ramifications for Volkswagen, which are expected to be substantial (the EPA can impose a maximum fine of around $18bn) it’s also called into question the ageing testing cycle used to measure a car's performance and raised a lot of concerns over diesel cars in general.  

So with the recent scandal very much still in car buyers' minds, is now the time to consider battery power? To help you decide, here we take a closer look at the main advantages of choosing petrol, diesel, hybrid and electric.

Diesel engines

The future of diesel looks a little uncertain at the moment. There’s a threat of additional charges for diesel-powered cars in cities and when a new test comes in, most predict CO2 figures will rise and fuel economy will fall, reducing the engine's main advantage over petrol.

As it stands at the moment though diesel offers greater fuel economy than petrol and usually cheaper tax costs too.

Compared with hybrid and electric cars they are usually cheaper to buy, but more expensive than petrol alternatives, the BMW 3 Series is one of the few exceptions. However now that the pump prices are a lot closer, the extra cost can be recouped much quicker.

It’s commonly accepted that diesel cars aren’t as quiet or refined to drive as petrol or hybrid cars, which if we discount the recent Volkswagen scandal, is one of its biggest drawbacks.

Who should pick diesel? High-mileage drivers and motorway commuters

Our diesel car choice: Audi A4 Saloon 2-litre TDI Ultra

At a glance...

The pros

  • More economical
  • Currently lower CO2 emissions so cheaper to tax
  • Refuelling takes minutes instead of hours to recharge batteries

The cons

  • Engines not usually as refined as petrol
  • More expensive price tag
  • Uncertainty surrounding possible legislation changes


Petrol engines

Petrol appears to have far more stability looking to the future than diesel and is in most cases the cheapest of all four options to buy. They are also arguably better to drive and more refined too.

Diesel may perform better on long motorway journeys at 70mph, but in the city petrol economy soon catches up and it’ll be interesting to see how close the two are when government tests are relaunched to reflect real-world driving next year.

Engine technology is advancing at such a rate that petrol engines are almost as economical as diesel cars these days, Audi’s cylinder-on-demand system (which can shut down half of the engine when not required) and Ford’s award-winning EcoBoost are both good examples.  

Who should pick petrol? Low-mid mileage drivers who need flexibility for occasional long distances 

Our petrol car choice: Ford Fiesta 1-litre EcoBoost

At a glance

The pros:

  • Better to drive
  • Historically offer cheaper fuel
  • Cheaper to buy
  • Refuelling takes minutes instead of hours to recharge batteries

The cons:

  • Higher CO2 means more expensive in tax
  • Lower fuel economy


Hybrid cars

Offering a combination of electric power and combustion engine, hybrid technology has been around since 2000 in the UK, however it’s only been the past few years when momentum has really been building.

There are a number of different types of hybrids available to buy, however for the purpose of this article we will be concentrating on plug-ins which can be driven on electric power alone for a certain amount of miles, after which the combustion engine (usually petrol) takes over.

Because the technology is still relatively new, in most cases it comes with a higher price tag. To help remedy this, the Government introduced a plug-in car grant a few years back which is up to £5,000 - check if the car you’re looking to buy qualifies here.

For a hybrid to save you money in the long run, you need to maximise the electric range. Hybrids perform their best in urban settings, on the motorway the electric range will drain quickly so if you’re a long-distance commuter, you’re unlikely to see any cost savings here.

If you live in London some hybrid cars will qualify to be exempt from the Congestion Charge if they emit less than 75g/km, saving you £11.50 per day, and the low CO2 emissions they produce mean lower tax bills over petrol and diesel too.

Who should pick hybrid? Low-medium annual mileage drivers with a daily commute under 20 miles 

Our plug-in hybrid car choice: Mitsubishi Outlander PHEV

At a glance

The pros

  • No fuel costs if driven on electric power
  • Minimal tax bills
  • Most are Congestion Charge free

The cons

  • Expensive price tag 
  • Unknown residual values 
  • Charging times 
  • Limited electric range 


Electric cars

Representing the best in terms of running costs, an electric car will cost you very little to run each year as there’ll be minimal tax to pay and no fuel costs to consider, plus if you live in London you’ll be exempt from the Congestion Charge.

They’re fun to drive when travelling from 0-30mph too as all the torque is available instantly unlike combustion engines, and it’s eerily quiet in the cabin which takes some getting used to.

Electric cars are expensive to buy though, even when you add in the Government's plug-in car grant and then there are range limitations to consider.

Even the latest electric cars will struggle to offer an official range over 130 miles per charge and that doesn’t take into account your driving style (harsh accelerating and braking will drain the battery quicker), what other systems are on in the car at the time (air-con for example) and any seasonal and terrain changes. For example, more power is needed to get the car started in winter and driving up hills will rapidly drain the batteries.  

The final big consideration is charging. Do you have a garage to store and charge your car overnight? Are there charging facilities at your work? Although the UK is lightly scattered with fast chargers at service stations, most of us will charge our cars at home using a wall charger or domestic socket and to get the battery up to full again can take up to ten hours. Remember recharging your car costs considerably less than visiting the petrol station though.

Who should pick electric? City drivers

Our electric car choice: BMW i3

At a glance

The Pros

  • No fuel costs
  • Congestion Charge free
  • Great to drive around the city

The cons

  • Limited range
  • Takes a long time to charge
  • Expensive to buy


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