Cheapest car to run – petrol or diesel?

Which is the best type of money saving fuel?

Why has the tide turned against diesel cars? Diesel used to be recommended as the best fuel for cars. Diesel cars were said to have better fuel economy and lower CO2 emissions than petrol cars. Owners of diesel cars were even able to pay a lower rate of road tax as a result.

But over the past couple of years diesel seems to have fallen out of favour. One of the reasons for this was that Volkswagen were found to have rigged the results of emissions tests, meaning that diesel car emissions – and also fuel economy – were not as good as had originally appeared.

It was also discovered that the nitrogen oxides produced by diesel engines increases in older diesel cars and this is having a huge effect on pollution, especially in cities.

Both these factors are affecting people’s’ views of diesel cars. In June 2018, the number of online searches for diesel cars fell to 47% of all car searches, as compared to 71% in June 2016.

But let’s take an objective look at the overall advantages and disadvantages of diesel cars.


Advantages of diesel cars

  • Diesel engines are more efficient and use 15−20% less fuel which means cheaper running costs.
  • Diesel engines have lower CO2 emissions than petrol. Diesel cars produced before April 2017 usually have cheaper car tax than petrol engines (though for newer diesel cars is is typically higher than for petrol).
  • Diesel cars have a stronger pull at lower speeds than petrol cars so have better overtaking power and towing ability. This is of real benefit if you regularly carry lots of passengers or cargo, or tow a caravan.
  • There are some excellent deals on diesel cars at the moment because of their bad press recently, so you could pick up a real bargain.


Disadvantages of diesel cars

  • Diesel cars usually cost more than petrol cars. Research from Which? shows that it can take 6-11 years to recoup the extra cost of a diesel over a petrol car.
  • Diesel fuel is more expensive than petrol, and servicing or repairing a  diesel car also tends to be slightly more expensive.
  • New diesel cars also cost more to tax than petrol cars, and various new charges, such as the London T-Charge and (form April 2019) the Ultra Low Emissions Zone, make it more expensive to drive diesels in certain cities.
  • Whilst diesel cars do have lower CO2 emissions, they do produce other emissions such as nitrogen, some of which are linked to breathing disorders such as asthma. Newer diesels therefore have a special filter called a diesel particulate filter (DPF) to help prevent pollution.
  • Diesel engines tend to be noisy.
  • Because of the increased car tax on diesels, and the new charges mentioned above, the resale value of diesels is expected to be lower in future.


As you can see from the above points, there are two sides to the story. The simple answer is that the best type of car for you really depends on the type of driving you do most.

If you do over 15000 miles each year and most of this is on motorways or dual carriageways, then it could still make sense to buy a diesel car because of the fuel economy you will achieve. But if you do a lower number of miles and tend to drive in towns and cities rather than motorways, a diesel may not be the best choice for you as the DPF pollution filter mentioned above can clog, and is costly to either fix or replace.

So choose your car wisely to make sure it is the best type for your needs.

Interestingly, the sale of new diesel and petrol cars will be banned in 2040. Which means that over the next 20 years there will be further change to the types of vehicles we’ll be driving and the advantages and disadvantages of each. Keep checking back here for more news of trends in cars, and for more money saving tips from Logbook Loans.