/ Motoring

Petrol vs diesel – which fuel is cheapest in the long run?

It’s hard to ignore the incessant sky-rocketing prices at fuel stations – diesel has tipped over the £1.50 a litre mark on many forecourts. With petrol 7p cheaper a litre, is diesel now a no-go?

With no sign of a let up in fuel price– and the possibility of a 3p fuel tax increase in August to rub salt into the wound – is now the time to ditch your diesel and go for an efficient petrol-engine car instead?

Although the 7p difference between petrol and diesel may not sound like much, it equates to nearly £4 more every time you fill up. For example, a Ford Focus hatchback with 55-litre fuel tank will cost you around £80.19 to fill up with diesel, but £76.34 with petrol.

If you only fill your tank up twice a month, it looks like you’ll be losing out on over £90 a year with diesel.

The cost of filling up my car

Even the cost of filling up a small car has gone up by more than a third over the past few years. As the price indicator on the fuel pump ticked swiftly past £60 when I was filling up my Renault Modus last night, I winced and was sorely tempted to stop – how could a supermini cost that much to fill up?

Yet, I’m still better off than plenty of other motorists right now. Why? Because my Modus has a petrol engine. If it had a diesel, it’d have cost at least £3 more.

So should I be smug about my fuel choice, or does the old adage about diesel cars being cheaper in the long run still hold true?

Having plugged the relevant info on my car’s purchase price, mpg, annual mileage and fuel price per litre into our clever petrol vs diesel calculator, I don’t really have that much to be happy about.

Does diesel pay in the long run?

Even with the current painfully high diesel prices, in just under two and a half years I’d be able to recoup the extra cost of filling up a diesel car over a petrol one. I’d even be able to recoup the extra cost of buying a diesel model.

Why? Because despite all the extra costs that come with diesel models, they always do more miles per gallon than petrol ones. For example, the 1.6 petrol Ford Focus averages 47.1mpg, compared to the 1.6 diesel stretching to 67.3mpg.

I drive over 12,000 miles a year, so spend an awful lot on fuel, That means going for a diesel model may well actually save me money in the long run, despite current prices. I’m certainly tempted.

If you’re thinking of buying a new car, how much are the current eye-watering fuel prices affecting your choice of diesel or petrol car?


I am planning to change my car in the next year and will have to decide on whether to stick with diesel or switch to petrol. My first diesel car was bought in 2002 when the main dealer was offering new Golf diesels at the same price as petrol models and the offer was too good to miss. My present diesel Golf was another new car that the dealer offered a good discount on, presumably to make way for new stock.

I would prefer to stick to diesel, but I drive only 7000 miles a year. What I buy will depend on what is on offer. I am not in any hurry to change my car and I will keep an eye on what is available from local dealers, whether that is petrol or diesel.


You’ve missed one essential consideration…depreciation. If you add up cost of ownership over a period, you’ll find that depreciation on anything but the oldest cars makes all other factors, including fuel costs, pretty insignificant for most drivers. (Insurance could be an even bigger hit for the young).

Most diesel cars depreciate more slowly than their petrol equivalents, reflecting their tendency to be longer-lived and (b) fuel cost is an even greater consideration for anyone buying an older car.

There are other things to take into account too, such as cost of servicing.

When replacing my car, I put together a simple spreadsheet to calculate cost of ownership of all the cars I’m considering. It includes factors such as cost of money (interest on a loan and/or loss of interest on capital), depreciation, road fund licence, insurance, servicing and fuel. The results are often surprising.

Keith Merry says:
16 March 2012

Can anyone please tell me why diesel in the UK is more expensive than petrol… Other countries that I have visited it has always been that diesel is cheaper than petrol..Are we being ripped off again?

Colin Samson says:
19 March 2012

The excuse for higher UK diesel prices is to do with lack of UK diesel refinery capacity. The UK cannot refine enough diesel for domestic supply, so has to import some refined diesel; this is more expensive. It seems that we are the victims of the recent success in UK sales of diesel cars; more refineries are needed but the fuel companies don’t want to spend the money required to build more . . . just yet.

D M L says:
17 June 2013

I am sorry to say I am old enough to remember when diesel was a lot cheaper than petrol in the uk but as more diesel cars became available, guess what, up went the price of diesel and it has never been below petrol again , can anyone confirm that diesel is actually cheeper to produce than petrol? or is Keith Merry correct it is yet another case of keep quiet and we will rip you off.

Robrt J Tucker says:
16 March 2012

No matter what we the motorists plan..albeit petrol or diesel ;.the Government will swap about to keep that which makes most revenue for the Government. if people stop buying Diesel.the Government will bump up the petrol prices..if we continue to use diesel the price will increase..to maintain revenue…
the answer is get 20 petrol or diesel Customers and buy up a block stock of either….or maybe get 50 motorists to block reserve a stock at bulk prices from the Oil Companies….I’m sure that will beat the Tax man..


For many years diesel was significantly cheaper than petrol, then overnight Diesel suddenly became much more expensive.

I think we need to look at why this sudden change came about and why non commercial Diesel is so expensive. I think at the time the Govt said that drivers of Diesel cars were gaining by having a higher MPG and to have cheap fuel as well was too much of a good thing.

I have just purchased a small diesel car for my wife with the sole intention of running it on cooking oil, which is considerably cheaper.

Top Driver says:
16 March 2012

You are falling into the trap that manufacturers want us to by quoting official fuel consumptions. The majority of motoring magazines do the same which makes their cost comparisons meaningless. In the real world official figures are pure fantasy. To use your example, I run a 1.6 diesel focus which has done 12,000 miles so is well run in yet even with gentle driving and 65mph cruising on motorways I only get 52mpg – nowhere near Ford’s claimed 67mpg. I prefer the superior pulling power of diesels but am seriously thinking of switching back to petrol but, for the reasons given above, i find it impossible to make any kind of true cost comparison.