Buying a new car? You know what make and model you want, but should it come in petrol or diesel flavour? Here’s all the information you need to make the right choice for you…
Find out which pump you should be heading for
With superior fuel economy and lower car tax liability, diesel cars might seem the obvious choice for cash-conscious motorists. However, with car makers putting ever-increasing premiums on the purchase price along with the development of super-efficient three-cylinder petrol engines putting them in the shade, is it really the smart move to buy diesel? The Crawley Down Group looks at the petrol vs. diesel facts.
Mileage: petrol and diesel prices matter
Price advantage of diesel is not so clear cut now
Once upon a time, diesel was the simple choice because it was much cheaper than petrol at the pumps. Sadly, that’s no longer the case with a per litre premium over unleaded petrol of around 6p. It’s not just the price of the fuel itself – buying a diesel car usually demands a premium of £1000 – £2000 compared with a petrol model of the same specification. With the new ultra-efficient range of small petrol engines hitting UK showrooms, the value of the diesel premium is looking increasingly dubious.
However, even with price increases, diesel remains the cheaper option when compared directly at the pumps, with the fuel itself costing around 5% more than petrol, but giving around 25% more mileage per tank
It’s also worth remembering that manufacturers get their official mpg figures under laboratory conditions, which don’t always reflect real-world fuel stats. What Car? magazine has a service called True MPG, where you can get these ‘real-world’ mpg figures that are built around your driving habits and routes (mainly motorways or A roads etc). Find the True MPG calculator here.
Your driving habits
The types of roads you drive on will impact on your choice between diesel and petrol
Choosing between petrol and diesel has a lot do with your driving habits; including how often you drive, how far you go and what sort of roads you use. It’s not just about the cost of the fuel, either. Repair bills will also be dependent on how much you use the vehicle. Here’s our quick guide to matching the type fuel to your personal requirements.
Annual mileage: If you’re considering a new car, then the number of miles you drive is an extremely important part of deciding between petrol and diesel. This relates to how long it will take the diesel’s superior fuel efficiency to offset its increased purchase price and higher price-per-litre cost. The exact amount of miles you will need to drive depends on the car you buy, but with 2013 Department for Transport figures stating the annual mileage for UK drivers was just 7,900, most would not benefit from owning a diesel. For example, a Ford Focus owner driving 8,000 miles would take three years to make money with a diesel version. However, a driver covering 12,000 miles a year would cover the initial diesel premium on the Focus by year two. The more expensive the car – the longer it’s likely take to recoup your cash.
Find out how many miles you’d need to drive to make diesel pay: Use this Which? tool to calculate how long it will take to cover the additional diesel premium you’ll be charged.
Driving time: Do you use your car for commuting, or other regular journeys? This will be another deciding factor between petrol and diesel models. If your journeys take less than 15 minutes to complete, then both types of engines will be pretty useless and negate cost-saving benefits of either fuel. As a rule, longer journeys will tend to suit diesel cars, but this will also rely on journey type. See our next point.
Type of road: If you’re winding your way through clogged city arteries with endless stop-start motoring, then diesel cars would traditionally be ‘less wasteful’ than petrols. However, new-style city cars with small, three-cylinder engines and diesel-shaming mpg figures are rapidly taking over. Add to this their low-CO2 emissions and equally low road-tax charges and it’s easy to see why many choose petrol over diesel for urban driving. However, if the majority of your motoring is on motorways and A-roads, then diesel is only option you should consider.
Congestion charge confusion: Another question mark over the wisdom of diesels for city drivers has been thrown into the mix by Boris Johnson suggesting owners are hit with a £10.00 surcharge on the London Congestion Charge. If brought in, it’s likely this would be replicated across many UK cities – effectively sounding the death knell for metropolitan oil burners.
Service costs and driving: Modern diesel cars must be fitted with a diesel particulate filter (DPF) to cut pollutants. While this will please EU bureaucrats, the new ruling has also cost diesel-car owners thousands in repair costs. Using a diesel for short journeys will result in the filter getting clogged and causing serious damage if not cleared. Most cars try to do this automatically, but if your journeys are too short, the process will be ineffective. If this happens, the warning light will come on. It is possible clear the warning light by driving for 10 minutes or so at speeds greater than 40mph. However, if this is not continuous the process will fail. If diesel drivers continue to ignore the warning light, the car’s performance will deteriorate and the likely result will be a trip to the garage for a new DPF – costing at least £1000. Just another reason why the type of journey you take should form a large part of your decision-making process.
Resale values: diesel v petrol
Will you keep more value with a petrol or diesel
What your car is going to be worth when you come to sell it on should also be considered as part of your decision when it comes to diesel or petrol propulsion. Diesels will usually hold their value better out of the two, but this may not always be the case. New, highly efficient, small-engined petrol cars will increasingly dent the high demand for oil burners – and therefore prices – by moving in on their unique selling points of mpg and low tax.
Many diesel cars will still be worth more than equivalent petrol models, but this won’t always be the case. Standard family faves such as the Ford Focus should certainly be a good bet for diesel buyers wanting to get a good return, but some more ‘fashion-led’ vehicles such as the Mini Convertible will certainly be more sought after with a petrol powerplant.
Compare resale prices using the What Car? Depreciation Calculator, where you can see how much diesel and petrol models will be worth in years to come – helping you make your decision.
It’s also worth remembering that while routine servicing costs are similar for both fuels, big problems on diesels can be far more expensive to rectify. Also, if your diesel is predominantly used for short journeys, you’ll find that problems such as clogged particulate filters can be a common problem. Other costs such as insurance are pretty much the same for both types of engine.
And finally… what are they like to drive
Don’t just make your choice on paper – go for a drive
We’ve left this to last, but what a car’s like to drive is possibly the most important element of any purchase decision. Apart from your house, your car will likely be the biggest investment you make – so saving a few pounds on mpg or resale costs should be put into perspective. Driving the car will be something you do on a daily basis – so why not let your heart rule your head on this one.
Don’t be ruled by old-school assumptions about diesels, for a start. Oil burners are no longer those clattery bus-like charabancs they once were – in many cases there’s no difference in refinement between diesel or petrol cars.
The big difference is how the two engines deliver their power, we won’t go into geek-like explanations about torque delivery, but, in short, a diesel car will provide a more relaxed drive with early and less frequent gearchanges, while a petrol-powered vehicle will give a high-revving exciting drive – with plenty of cog-changing action. As a result, lots of motorway cruising on motorways can be a chore in a sporty petrol, while a laidback diesel will be just the job. However, twisty country lanes or nippy city traffic driving could be far more satisfying in a petrol. This is why you should never make your decision on facts and figures alone.
Book your book a test drive and make your choice where it counts – on the road.