Opting for a used petrol car is likely to be much more cost effective than the equivalent diesel model, according to new research. We take a closer look.
Motorists have a tough decision to make when it comes to choosing between a petrol and diesel engine.
Petrol cars are normally a bit cheaper than their diesel counterparts, but the latter use less fuel.
On this basis, the greater the number of miles you drive, the more likely you are to save money with a diesel.
Fuel factors to consider when buying used
There is also the cost of the different types of fuel to take into account.
Diesel is currently more expensive than petrol in the UK, and the wider the price gap, the longer it will take diesel drivers to recoup their extra initial expenditure.
But new research from secondhand car website UsedCarExpert.co.uk appears to have tipped the balance even further in favour of petrol engines.
Its analysis suggests that opting for a used petrol car is likely to be much more cost effective than the equivalent diesel model, even if there is a significant gap in fuel efficiency.
Petrol versus diesel
UsedCarExpert's Matt Tumbridge explains: "Take a three-year-old, five-door, Ford Focus, which is pretty typical family transport.
"On paper, the 1.6 litre petrol unit manages just 48 mpg (miles per gallon) whereas the 1.6 litre diesel engine manages 64 mpg.
"Yet surprisingly, the petrol engine is actually the better buy for most people."
Why is petrol a better buy?
Firstly, there is the purchase price of the two cars.
In our example, the used petrol Focus costs £8,000 while the diesel is 10 per cent more expensive at £8,854.
And, in fact, this price gap is likely to be even wider than when the cars were sold as new.
To take a current example, a petrol Ford Focus 105 Zetec 1.6 litre would cost £17,305 new according to car buying site WhatCar.com.
But its diesel counterpart would set buyers back £17,895: a gap of £590, or 3.4 per cent.
Tumbridge says it is typical for petrol cars to depreciate faster in the first few years, thus making them better value on the secondhand market.
Closing the price gap
So what prospective used car buyers need to work out is how long it would take to make up this £854 difference.
What that really depends on is how many miles the driver does each year.
The UK average is around 8,000 miles per year, according to the latest Department for Transport figures.
For the petrol Focus doing 48mpg, this would result in a fuel bill of £1,015 in the first 12 months, compared with £790 for the more efficient 64mpg diesel model.
This is based on a petrol price of 134p a litre compared with 139p per litre of diesel.
No savings until year three
Take into account the fact that the diesel car's annual vehicle tax would be £100 cheaper due to its lower carbon emissions and this means it costs £325 less to run than the petrol model in the first year.
But this saving doesn't offset the diesel car's higher price tag.
Tumbridge says: "This means the petrol driver is £529 up in the first year and still £204 up after two years.
"It takes until the end of the third year for the diesel to be justified as the cheaper choice."
High mileage drivers can save with diesel
A diesel driver who covered 12,000 miles a year, however, would save almost £440 on running costs in the first year, and offset the £854 higher price tag in the second.
Tumbridge adds: "Used Car Expert has conducted this research on most popular makes and models.
"We found that in most model ranges, petrol-engine cars are noticeably cheaper than their diesel equivalents, and despite giving away 10 to 20 mpg are still the better buy for many motorists.
"Only motorists who keep their car longer than three years or do very high mileage win with diesel cars in the current market."
Watch out for car maintenance costs
As a final warning, Tumbridge says that buyers should also take into account the differences in paying for the maintenance of older vehicles.
"All this analysis overlooks that diesel servicing costs will be higher," he adds.
However, some experts say that although servicing a diesel engine may be more expensive, this has to be done less frequently and overall the costs even out.
Fuel cost calculator