/ 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?

Essexman says:
20 March 2012

I think the reason diesel’s cheaper in much of Europe is that the fuel duty on it has been less there than it is on petrol, whereas in the U.K. it’s the same for both. So even when the base price of diesel is higher than petrol (most of the time these days!), it’s still cheaper in say, France & Spain. I’m not sure the non polluting electric car argument is sound, the electricity has to be generated somehow & it’s not all hydro/wind/solar. But it’s a start & better breathing exhaust fumes in the high street. They (electrics) still have one very big problem though, limited range – and they get even worse in cold weather.

Brian says:
20 March 2012

Diesels used to be reliable to very high mileages, but the modern diesel with turbochargers, particulate filters, dual mass flywheels etc – all neccessary to comply with emmission regulations – give expensive problems that can wipe out any potential fuel saving.


How does the cost of servicing compare for petrol and diesel engined cars?

I took my VW Golf 4 into the main dealer a couple of times when it was new (they did a poor job in my opinion) and apart from having the timing belt replaced I’ve done the servicing myself.

I know what’s involved in servicing my 10 year old car but plan to hand the job over to a garage and would like to know about servicing costs for modern cars, which may be a factor in deciding to buy a new petrol or diesel car.


Servicing costs are very variable. Phone a few dealers. Many offer packages up-front for very reasonable prices, e.g. £350 for 5 years on a BMW 3-Series or £400 on a 5-Series.

These typically only cover the basics, like oil, brake fluid, spark plugs and filters. You’ll still have to pay for brake discs and pads, etc. The packages are transferable, I think, so if you sell before the 5 years are up you have a powerful selling tool.

Several manufacturers offer free servicing for a number of years. Phone or visit a few dealers or check manufacturer websites.

Keep in mind that service intervals are longer than they used to be. Many modern cars have variable intervals and advise you via their displays, based on the sort of driving you do, when the next service is due. In the case of BMW, you can go anything up to 18,000 miles between services, if your journeys are mainly long ones on the open road.


18,000 miles between services?? That’s plenty of time for damage due to stone chips, split CV joint boots, etc to go unnoticed. I wonder how many cars are unfit to be on the road.

Of course users know that they are responsible for ensuring that their car is roadworthy at all times.

Thanks for the advice on checking what dealers include with the cost of a car.


Are you telling me you’re not smart enough to spot stone chips for yourself? In any case, do you really believe that garages check for stone chips, or even boot splits, as part of an oil change service (which is all many services are)? As for all those unfit cars, what do you imagine the MoT test is for?

Do you realise that many people do 18,000 miles in 6 months? Their cars will be serviced twice p.a. Those who take much longer than a year to do 18,000 will be told by their OBC that a time-based (rather than mileage-based) service is required. And, between services, cars over 3 years old need annual MoT certificates; a split boot means a fail. Just how often do you reckon should safety checks be carried out?

I’ve had my 5-Series diesel for 6 years from new and it’s had nothing other but four routine services. There have been no split boots…no faults at all, in fact. The extended warranty I paid for was a waste of money. It sailed through its MoT yesterday. I suspect the battery is on its way out, but that’s about it…apart from some stone chips, not that my garage has ever pointed them out.

You say your car is 10 years old. It sounds as though your thinking may be out of date. I took the trouble to reply with what I imagined was good news but you don’t want to hear it. How sad.


Sorry Aitch, I meant stone damage rather than stone chips to paintwork or glass.

I may be out of date and only an amateur mechanic but my life depends on my car being in a safe state. The mechanic who has occasionally done repairs on my car deplores the infrequent servicing recommended by manufacturers and I trust what he and others who hold the same view have to say. Look a the percentage of cars that fail the MOT.

I do not know how often safety checks should be carried out and perhaps we should be guided by those who carry out MOT inspections.

Anyway we have a different outlook, so let’s end the discussion.

Essexman says:
20 March 2012

The cost of servicing isn’t much more with diesels than petrol’s in my experience, though the more cramped engine bay of the diesel should mean higher labour costs in theory. The fuel filter, a serious piece of kit in a diesel will need to be changed more often though.

But Brian has it right, a lot more to go (very expensively) wrong in the modern diesel. Not that it necessarily will. Failed turbocharger (now fitted to all diesels) seem to crop up a lot, often caused by missed or late oil & filter changes. Insist on a synthetic oil come service time & get it changed once a year, or better still, every 6 months. And if you do it yourself (check Halfords online for right grade)you can be sure you get the oil you’ve paid for in your sump.