We’ve never had so much choice when it comes to what powers our cars, with the traditional petrol and diesel-fuelled internal combustion engine options now joined by a wide range of hybrids and several pure electric vehicles.
In this guide we’ll explain the benefits and drawbacks of each fuel type, as well as identifying the kind of drivers to which each type is typically best suited.
Although even the most efficient petrol cars can’t match the economy of a diesel on a long journey, they are quieter and smoother at low speeds and when accelerating, and they also have a higher rev limit, which can make them more exciting to drive.
In addition, there’s been a trend in recent years to build smaller, more-efficient petrol engines and then equip turbochargers to boost performance. This, along with technology that can cut the engine when the car is stationary, has helped to reduce CO2 emissions (and thus tax costs) of some petrol-powered new cars to almost diesel-like levels.
Petrol cars also tend to be less mechanically complex than diesels and hybrids, which makes them cheaper to buy and maintain. Petrol fuel cost is lower than diesel, too.
Best for: Drivers who cover an average annual mileage with a mixture of long and short journeys will be best served by a petrol car. As a rough guide, if you drive fewer than 15,000 miles per year, it’s likely petrol will be the cheaper option.
If you cover a high annual mileage with a lot of motorway driving, choosing a diesel car still makes a lot of sense. Although the diesel engines aren’t as smooth as a petrol or hybrid at low speeds, they require fewer revs at 70 mph, which results in quieter motorway cruising and superior fuel economy. As a result, you can expect to travel approximately a third farther per tank in a diesel-powered car than you would in the equivalent petrol model, which can lower running costs for high-mileage drivers.
Diesel cars also offer excellent mid-range pulling power, meaning you don’t need to change gear as often and they tow well.
However, while the Government encouraged sales of diesel cars for their low CO2 output, attention has now shifted to how the other harmful emissions they produce contribute to poor urban air quality. As such, plans are in place to ban diesels from some city centres (Paris, Madrid, Athens, and Mexico City plan to be diesel-free by 2025), while in other areas local authorities charge diesel owners a surcharge for parking, all in a bid to discourage their use.
Throw in potentially expensive maintenance costs for complicated emissions equipment on used diesels, and you start to see why some believe their resale value could take a tumble in years to come. That said, it is also worth pointing out that because Vehicle Excise Duty (or “road tax” as it is often called) is linked to CO2 emissions, diesels are still cheaper to tax than their petrol equivalents – a trend that’s echoed when it comes to company cars, even with a 3% diesel levy in place.
Best for: Diesels are ideal for high-mileage drivers and company-car users, plus those who regularly tow.
Mention hybrid cars and you might well think of the Toyota Prius. However, while Toyota gained a huge initial lead on rivals in this field, most other manufacturers now offer some kind of hybrid option.
Hybrid vehicles use a conventional engine (usually a petrol engine) along with a battery-powered electric motor to lower a car’s emissions in official fuel tests and offer a “best of both worlds” approach that combines the quiet running of an electric vehicle with the fuel range of a petrol one. Hybrids are generally at their most efficient during in-town driving, but can’t match the mpg figures of a diesel or petrol engine on the motorway.
Until recently, the pure-electric range of a hybrid was a mere mile or two. However, the arrival of plug-in hybrid (PHEV) cars with much bigger batteries has increased that figure on some cars to approximately 30 zero-emission miles before any petrol power (or a recharge from an external source) is required. Plug-in hybrids have proven popular, but have attracted some controversy as they can be less efficient than an equivalent petrol or diesel car if they aren't regularly plugged in.
Very low emissions of CO2 make hybrids among the cheapest cars in terms of Vehicle Excise Duty, which in turn means that those with a low retail price can also make affordable company cars.
Some modern petrol and diesel cars incorporate what's called 'mild hybrid' technology into the powertrain. Unlike a full-blown hybrid, these cars can't really run on electric power alone as they don't have a big enough motor. Instead, a larger battery and a very small electric motor are incorporated into the petrol engine, harvesting kinetic energy when cruising and braking and then redeploying it to provide an extra surge of power when the engine needs it. The system can also assist the engine while it's shutting off and starting up again at traffic lights or junctions, which all helps improve fuel consumption.
These mild hybrids are, generally speaking, a little more fuel efficient than a petrol or diesel car of equivalent power, but they aren't usually as economical as full or plug-in hybrids.
Best for: Hybrids are good choices for low-mileage drivers who spend a lot of time in urban areas or company-car users who stick to the less-expensive options.
In addition to petrol, diesel, and hybrid, there is an increasing number of pure electric vehicles (or EVs) now on sale. These make do without any kind of engine and instead use a much larger battery and at least one electric motor to provide a driving range between charges of anywhere from 80 to 300 miles, and sometimes even more, depending on the car.
What’s more, because these electric motors are able to deliver 100% of their power the moment you touch the accelerator, they feel very responsive to drive in comparison with petrol or diesel cars, and they are also extremely quiet. And, fo course, there are no tailpipe emissions. In fact, there's no tailpipe.
At present the charging infrastructure is still growing (and charging itself takes significantly longer than filling a car with fuel), making most electric cars less suitable for drivers who cover a lot of miles. However, those interested in electric motoring will be pleased to note the Government is encouraging their uptake via grants to reduce their sometimes-high purchase prices.
There's also a Government grant available to reduce the cost of having a charging point installed at your home, and combined with the long range of some of the latest models, this can mean you very rarely, if ever, have to use public chargers.
Best for: Those who can charge at home and drive mostly short distances should consider owning an electric car. Anybody travelling into London will also appreciate that electric cars are exempt from the Congestion Charge.
Updated on: September 22 2020