Petrol or diesel? It’s one of the first questions you should resolve when buying a new or used vehicle. Most vehicle manufacturers offer both options with some models available as petrol- or diesel-electric hybrids.
Your choice of fuel will depend on your budget, circumstances and preferences. In general diesels have been the preferred choice for frugal motorists due to greater fuel economy and lower car tax. However as diesel emissions are being carefully scrutinised, manufacturers demanding a premium for diesel models, and petrol engines are becoming much more economical, is diesel really the answer to cheaper motoring?
Historical thinking that diesels being less refined and cheaper to run has become outdated, as technology closes the difference between the two fuels. In short, diesel isn’t always best for fuel improved mpg and petrol vehicles are not always the most fun to drive.
There are four factors main factors to consider before making your purchase between a petrol vehicle or a diesel vehicle:
- Petrol or Diesel – which is cheapest?
- Fuel Economy
- Running Costs
- Driving Preference
- Petrol or Diesel
To decide which is the most economical option, look first at the difference in purchase price between the petrol and diesel versions of the vehicle you are purchasing Most manufacturers still charge more for diesel, you can pay anything from £1,000 to £2,000 more for make and model with the same specification.The main thing to consider is will you get the difference in price back if you pay the extra for diesel? To do this you must consider the running costs of the vehicle you are purchasing mainly fuel economy, fuel costs and road tax.
- Fuel Economy
Diesel cars in general will give you more mpg, the more miles you travel, the more money you will save from the better fuel economy given by diesels. However with the average UK motorist does than 9,000 miles per year so potential fuel economy savings aren’t that great.Due to UK oil refineries concentrating their efforts on producing petrol in recent years, diesel is dearer in the UK than it is in other European countries; where CO2-related tax structures also add to diesel appeal (CO2 output being directly related to fuel consumption).
A petrol vehicle can give you up to 30% less mpg than a diesel equivalent, but the diesel vehicle might end up being more expensive to run over three years when you take into consideration purchase price, fuel economy, fuel costs and road tax.
- Running Costs
Running costs are a greater issue than the mpg you get. These costs include the non-fuel factors such as servicing, insurance, purchase price, road tax and depreciation – all of which can vary considerably between petrol and diesel versions of the same vehicle.Diesel vehicles tend to be more expensive to purchase and maintain than their petrol counterparts, although the ‘diesel premium’ reduces in relative terms as cars get bigger.
The most overlooked factor in running costs is age. Depreciation is the largest cost for all motorists to consider, resale values play a huge part in deciding whether a petrol or diesel vehicle will be more cost-effective choice for you.
Diesels are generally cheaper to tax and insure. It is also true that the more miles you travel; the more money you will save by choosing diesel engine rather than a petrol engine.
- Driving Preferences
If you last drove a diesel vehicle 5 or 10 years ago, you will find that engineering advances have improved diesel engines so much both in performance and refinement.A diesel develops maximum torque – the ‘shove’ you need to pick up speed – at lower engine revs, allowing you to change up through the gears quicker This relatively narrow power band can make manual gear changes a chore, but modern automatics work very well with diesel engines.
Today’s diesel engines can be smoother than petrol engines too – especially the two- or three-cylinder petrol units that are a popular choice for manufacturers looking to boost mpg.
Good diesel engines are currently around 35% efficient, petrol engines are around 27%, efficient but many vehicle manufacturers are closing the gap by producing petrol engines with diesel-like torque, and diesel engines with petrol-like response. New-generation petrol engines are becoming smaller, lighter and more efficient, with no loss of performance.
One important factor to bear in mind when choosing diesel is the increasing use of diesel particulate filters (DPFs). In mixed driving, these filters work fine, but if your lifestyle is mainly town-based, you should think carefully before buying a DPF-equipped car. A diet of low-speed urban motoring will clog DPF filters.