Diesel vehicles produce more small particulates which can be damaging to your health. However, modern diesels are fitted with Diesel Particulate Filters (DPFs), which capture these particulates, stopping them from being expelled through the car’s exhaust pipe.
It is worth bearing in mind that DPFs can can become clogged if you tend to do more city driving; they perform much better with a good mix of motorway travel in there too, so if that isn't you it could be wise to avoid diesel.
When it comes to emissions, petrol cars tend to produce more carbon dioxide (a greenhouse gas that is contributing to climate change), while diesels spurt out more nitrogen dioxide which can be responsible for smog and respiratory problems.
Some modern diesels use a chemical called Ad Blue, which reacts to nitrogen dioxide so that it leaves the exhaust as nitrogen and water vapour, lessening air pollution. The Ad Blue goes in to a separate tank from the diesel and needs topping up every couple of thousand miles.
Ultimately, whichever fuel you burn will have a detrimental impact on the environment.
On the Road
Petrol engines tend to be quicker off the mark and deliver faster 0-60mph times whereas diesels have more torque and so will accelerate faster in higher gears, making things like motorway overtaking easier.
Many people have preconceptions about their preferred fuel but the truth is developments of engines over the past 5 to 10 years have seen the two fuels move much closer together in their performance. New petrol engines are becoming more efficient and capable of producing the same torque as diesel engines, similarly turbo diesel engines are often able to provide petrol-style performance.
Diesel engines have a reputation for being noisier and less smooth although, as with some other points on this list, this is much less true with modern cars. If you haven't tried driving a more recently built diesel you might just be surprised. Similarly you can still expect petrol engines to generally be quieter but the gap between the two is shrinking all the time. When it comes to the fuel itself remember diesel is smellier than petrol and can be difficult to get off your hands if you get them dirty when refueling.
Purchase Price and Depreciation
Generally speaking, diesel cars are more expensive to buy or lease, but this is not always the case and it pays to do your own research on the models you're interested in. There are concerns that second hand values may drop off in the coming years as appetite for diesel cars is dampened by potentially punitive taxes but of course when you lease a vehicle this risk is borne by the funder so there's no need to worry.
Diesel tends to be a couple of pence more per litre at the pump but will generally get a few extra miles per gallon. Unfortunately it can be difficult to calculate the actual mpg you'll achieve in the real world as it depends on the routes you take and your driving style, however it's worth having a go at calculating how much you think you'd spend on fuel and then comparing the two.
Insurance and Tax
When it comes to insurance you may find that insurance premiums are lower for diesel cars; it's always worth checking and comparing the vehicles you're interested in.
Previously, road tax on vehicles varied more widely and it was possible to save money by choosing some cleaner diesels, however since April 2017 most cars will pay a flat £140 each year after the initial year.
Remember when you lease a car from Leasing Options car tax is included in your monthly rental.
Understanding the Road Fund Licence (Car Tax)
The way that the Road Fund Licence (commonly called car tax) works is quite simple - for new cars, you’ll pay an initial payment in the first year which is based on the CO2 emissions of the car. The following years are always charged at a fixed price of £140. All diesel engines have a £5 additional charge on top of everything for each year, including the first.
An exception is if the P11D of the car at the point of registration is over £40,000 - in this scenario, the first three years following its registration are supplemented by £310. This means that for all cars worth over £40,000 when registered will pay £450 in car tax for three years.
If the car is a hybrid or runs on an alternative fuel source, you’ll get a discount of £10 on the first year’s charge and every year after that. Zero emissions cars like electric or hydrogen cars have £0 tax unless the car is valued over £40,000, in which case you’ll have to pay the £310 supplement for the first three years.