Fuel economy - petrol vs diesel | The Car Expert (2023)

Fuel economy is a major consideration when buying a car. One of the most common questions car buyers in the UK ask, and certainly one I have been asked many times, is “Should I buy a car with a petrol or diesel engine?” Well, there’s no simple answer; it depends on a number of factors. In this article, we’ll explore this in more detail.

Many car buyers have got themselves tangled up in false economic arguments when trying to choose between a petrol or a diesel engine when buying a new or used car.The correct choice is very much dependent on your specific circumstances and driving style.It is very importantto carefully and thoroughly analyse yourcar usage to get a clear understanding of what yourneeds are.

For this article, we are not considering hybrid or purely electric cars, because it complicates things massively and will be the subject of a separate article later on, but let’s consider a straightforward example of diesel vs. petrol.

(Video) Electric, hybrid, petrol & diesel explained & compared!

The Volkswagen Golf has long been considered the benchmark for mid-size hatchbacks, and is available in a range of petrol and diesel engines with identical specifications.This makes it a good example to compare the engines.For this example, we will compare the 1.4 TSI 122hp petrol engine with the 2.0 TDI 140hp diesel engine.In the real world, these engines give comparable overall performance.We will compare manual gearboxes and assume the customer has paid full retail price.Servicing and maintenance costs are broadly comparable between the two models, so the difference will really come down to the engines.

We will use the official urban and combined fuel economy figures as provided by the government (extra-urban figures are usually useless), and assume the buyer keeps the car for three years, covering 10,000 miles per year. Resale value is provided byWhat Car?magazine. Fuel prices are provided bypetrolprices.comas of today (5 March 2012). We have to assume that fuel and registration costs stay at 2012 prices for the next 3 years (if only!) and that insurance costs are broadly similar for each car (which they should be).

(Video) Diesel Vs Petrol Engine: Which one is right for you? | Auto Expert John Cadogan

Petrol:

  • Golf Match 1.4 TSI 122hp – £19,100
  • Value after 3 years – £7,640 (40% of new car price)
  • Fuel economy, urban – 34.4 mpg
  • Fuel economy, combined – 45.6 mpg
  • Road tax (first year included in new car price) – £130/year

Diesel:

  • Golf Match 2.0 TDI 140hp – £21,090
  • Value after 3 years – £9,491 (45% of new car price)
  • Fuel economy, urban – 46.3 mpg
  • Fuel economy, combined – 58.9 mpg
  • Road tax (first year included in new car price) – £95/year

So the diesel car is more expensive by nearly £2,000 when new, but should be worth about £1,800 more after three years. It costs less to register (£35/year at present, so not a lot in it) and should use less fuel on average.

Total cost of buying and running each car for three years (excluding insurance, servicing and maintenance) are as follows:

Petrol:

  • Using Urban fuel economy figures – £17,335
  • Using Combined fuel economy figures – £15,964

Diesel:

  • Using Urban fuel economy figures – £16,293
  • Using Combined fuel economy figures – £15,300

So the diesel Golf is £347/year cheaper to run using the urban figures, and £221/year cheaper to run using the combined figures.In the overall of a £20,000 car, this is hardly a significant difference, and doesn’t take into account individual driving circumstances.The government fuel economy tests are not really representative of real-world driving, and very few drivers ever match the official figures.Below I will detail the differences in the way a petrol engine drives compared to a diesel engine.

(Video) Petrol -vs- diesel in Australia in 2015 | Auto Expert John Cadogan

What can be said for certain is that the higher your annual mileage, the better the diesel becomes.The above calculation is based on 10,000 miles per year, which is considered average.If your mileage is higher than that, the diesel car’s advantage is greater.If your mileage is lower, the figures become even closer.

The above example is also very specific to that car and those two engines. If you are looking at a different car, then you need to use the relevant figures for the engines available for that model.

What is most important of all is properly considering how you will really use the car for as long as you own it, but here is a very general breakdown of the generic differences between petrol and diesel engines:

(Video) Does Fuel Consumption Really Matter? | Auto Expert John Cadogan

  • A petrol engine usually produces more power than a comparable diesel, making it more responsive at very low revs, so pulling away from rest at the lights or at a T-junction is usually quicker in a petrol engine. A diesel engine will have to work harder and therefore use more fuel to keep up.
  • A diesel engine usually has more torque than a petrol engine, making it better at carrying heavy loads. So a diesel engine maintains its performance and economy much better when you load up a car with a full load of passengers and a bootful of luggage, whereas a petrol engine will struggle noticeably in comparison, losing performance and using more fuel.
  • A diesel engines tends to be more economical in steady-state driving, such as on a motorway, when the engine is at its optimal point and cruising along comfortably. A petrol engine will have to work harder to maintain its momentum and will use more fuel.
  • Stop-start town driving is inefficient for any kind of engine, so there is much less difference in fuel economy between a petrol and diesel engine around town. Especially if you have to work the diesel engine harder under acceleration.
  • A petrol engine produces fewer overall emissions per litre of fuel burned than a diesel engine. But a diesel engine will usually use fewer litres, so be may more eco-friendly for a given distance (internationally measured in grams per kilometre – g/km). But that’s assuming optimal conditions, because…
  • Short journeys are very inefficient for any kind of engine, as cold engines use more fuel and pollute a lot more than warm engines. This applies to both petrol and diesel engines, and means neither engine approaches anywhere near its ‘official’ fuel economy figures. A journey has to last at least 10-15 minutes before the fuel economy starts to hit its best figure, and prior to that both engines are using lots of fuel.
  • Diesel-engined cars tend to cost more than petrol-engine cars when new. However, their resale value is usually better (this is very dependent on fuel prices at the time, so is only ever a prediction of what will happen in the future).
  • The sound of a diesel engine is still off-putting to some people, although they are much more refined than they used to be.

More than just fuel economy

We need to take all of the above into account when deciding whether to go for a petrol or diesel car. Funnily enough, the recommendations provided by The Car Expert are split about 50/50 for petrol and diesel, with factors other than fuel economy often being more important. Also, if you’re going to buy a used car, there may be very little difference in price between a petrol car and a diesel car. But the overall message is to carefully evaluate how you are going to use the car before laying down your hard-earned money.

Want to know more about fuel economy? Read The Car Expert’s latest article on why your real-world fuel consumption doesn’t match the official manufacturer figures.

(Video) Diesel vs Petrol – what you need to know | Top 10s

Want to know more about the specific issues for using a diesel car for city driving? Read The Car Expert’s article on diesel cars and urban driving.

Should you pay extra for premium fuels?The Car Expert looks at premium diesel and premium unleaded petrol, and whether they’re worth the money.

Was this article helpful? Please take a second to like it and it with your friends on Facebook, Twitter, Google+, Reddit or LinkedIn. Thank you :)

(Video) Gasoline (Petrol) vs Diesel: Which one is better? A Beginner’s Guide

FAQs

Which has better fuel economy diesel or petrol? ›

Diesel engines are generally more efficient at burning fuel than their petrol counterparts. Depending on the car as well as the engine used, a diesel engine uses 15-20% less fuel compared to a petrol engine. However, the price of this efficiency is a higher premium compared to the petrol variant of the same car.

Should I buy petrol or diesel car in 2022? ›

Put simply, you should buy a diesel car if you regularly cover a lot of high-speed miles, i.e. a regular motorway commute rather than lots of short trips. Diesel cars give better fuel economy than their petrol counterparts, as well as offering more torque on tap for those who want to tow or the like.

Is it worth buying a petrol car in 2022? ›

Petrol and Diesel cars are more sustainable and 'cleaner' than they were 10 years ago, making them still a brilliant choice in 2022. Don't be overwhelmed by the new electric market coming in strong and think you are obliged to go and buy one to be more eco-friendly.

Do you get better fuel economy with diesel? ›

Diesel engines are typically much more fuel-efficient than gas engines, even those with very high compression ratios. Diesel fuel is also more energy-dense than gasoline, meaning more energy per gallon. As a result, it's not uncommon for a diesel-powered car to get 50 mpg or higher.

Why more petrol cars are better than diesel? ›

Petrol engines produce less pollutant particulate matter. Hence, they are less harmful to the environment. Diesel engines produce more pollutant particulate matter. Hence, they are more harmful to the environment.

Should I get petrol or diesel car? ›

Diesel has its major advantage of low fuel cost and better mileage but when it comes to service and maintenance it will cost you more than petrol.

Is it worth keeping a diesel car? ›

Diesel drivers know the benefits, primarily a far larger range than petrol (and certainly electric cars) because of much better fuel economy. If you drive a lot of motorway miles, diesels still make sense, and because of their better pulling power are best if you need to tow caravans or trailers.

What happen to diesel car after 2025? ›

All cars in Singapore have to be registered before they are allowed on the roads. This means that there will be no new diesel cars and taxis from 2025, and no new internal combustion engine cars and taxis from 2030.

Do petrol cars have a future? ›

Petrol or diesel car in 2022 – Conclusion

The answer would be a yes, as the future of ICE vehicles seems safe at the moment. It also seems that buying an ICE car makes sense for the next few years. After that, we will have to wait on how the market is developing regarding EVs.

Should I wait for 2022 to buy a car? ›

While soaring used car prices are bad for those who can't afford a new car, they may mean 2022 is a good time to buy a car for those with a vehicle to trade in. A high trade-in price means added capital that can help reduce the finance share of purchasing a new car.

When should I stop buying petrol cars? ›

The diesel petrol ban only applies to the sale of new cars. So you should still be able to buy second-hand petrol and diesel cars. Don't expect prices for petrol and diesel cars to drop after the 2030 ban though.

Should I sell my petrol car now? ›

When should I sell my petrol car? Although the petrol car ban may seem far away, it's could be best to start thinking about selling yours sooner rather than later. Petrol cars are becoming increasingly unpopular, and with the government planning to ban them by 2030, their value is likely to drop significantly.

Is petrol or diesel better for longer journeys? ›

Due to their better fuel economy, diesels are often preferred for longer journeys. Diesels also accomplish greater power with lower engine revs unlike petrol too, making them perfect for long motorway journeys. Surprisingly, petrol engines do indeed emit more CO2 compared to their diesel counterparts.

What is the disadvantage of diesel cars? ›

Cons of diesel cars

Diesel fuel usually costs more. Servicing can be more expensive, although you don't need to do it as often. Diesel cars produce a lot more NO2. Diesel engines can be slightly noisier.

Is diesel better for longer journeys? ›

Diesel is also better for longer journeys because of it's on-average increased fuel economy.

Which engine is more reliable diesel or petrol? ›

Diesel cars are more than three times as likely to break down as their petrol counterparts and will typically cost 20% more to fix when they go wrong.

What will happen to diesel cars after 10 years? ›

But a diesel vehicle cannot ply in Delhi beyond 10 years in terms of court orders. However, NOC can be obtained for diesel vehicle beyond 10 years but less than 15 years for [other] states which have conveyed their concurrence for registration of such diesel vehicles.”

Is diesel still good after 2 years? ›

As for diesel, it can remain usable for between six and 12 months before becoming 'gummy' which, if used, can clog up filters and cause you issues with your engine.

Do diesel cars have a future? ›

In the interim, diesel engines will continue in some segments, and eventually, there will be a shift towards cleaner fuel. Some automakers still see a future for diesel engines. Diesel is still a major component of automakers like Mahindra, Toyota, Jeep and KIA due to their SUV/MUV/Crossover product portfolio.

Can you still drive petrol cars after 2040? ›

What happens to cars after 2040? You will still be able to drive a petrol or diesel car following the ban in 2040. The restriction only affects new cars registered after that date. Cars registered after 2040 will have to be 0 emissions vehicles.

Can I buy a diesel car after 2030? ›

Can I still buy a second-hand petrol or diesel car after 2030? Like the above, the ban only affects the sale of new vehicles, so you'll still be able to buy and sell used petrol or diesel cars after 2030. For the same reason, you'll also be able to buy and sell used hybrids after 2035, too.

Can you drive a diesel car in 2030? ›

Can I still drive a petrol and diesel car after 2030, and a hybrid with a "significant" zero emission range after 2035? Yes. The bans on these dates only apply to sales of new cars, and there are no current plans to outlaw the use or sale of second-hand cars based on these criteria.

Will diesels be banned? ›

Even if your petrol or diesel car is still running in 2030, there are no plans to ban it from the roads entirely, as second-hand sales are expected to be unaffected.

Is diesel going away? ›

New models would be zero-emission in 2024, while diesel and gas drayage trucks must retire after 18 years to guarantee that they meet a zero-emission requirement by 2035.

Are petrol cars in decline? ›

Despite a significant decrease in market share for internal combustion engine-type vehicles, petrol remains dominant at 27.39 per cent, with diesel accounting for 25.92 per cent of registrations. Hybrid sales are at 24.23 per cent, with electric and plug-in hybrids at 11.66 per cent and 8.01 per cent respectively.

What car should I not buy in 2022? ›

10 Cars To Avoid In 2022 And Why
  • 10/10 Toyota Mirai.
  • 9/10 Tesla Model Y.
  • 8/10 Maserati Ghibli.
  • 7/10 Lexus GX.
  • 6/10 Mitsubishi Mirage G4.
  • 5/10 Subaru Ascent.
  • 4/10 Ford EcoSport.
  • 3/10 Chrysler 300.
14 Feb 2022

What should you not say to a car salesman? ›

5 Things to Never Tell a Car Salesman If You Want the Best Deal
  • 'I love this car. ' ...
  • 'I'm a doctor at University Hospital. ' ...
  • 'I'm looking for monthly payments of no more than $300. ' ...
  • 'How much will I get for my trade-in? ' ...
  • 'I'll be paying with cash,' or 'I've already secured financing. '
19 Aug 2019

Will car prices go back down in 2022? ›

Used car prices are already starting to drop as the market cools, having seemingly peaked in early 2022. On the other hand, new vehicle prices are unlikely to drop in 2022 due to persistent inflationary pressures. “There's still a lot of inflation bubbling up in the new vehicle supply chain.

Will petrol cars be worthless in 5 years? ›

The petrol and diesel car ban only affects sales of new vehicles, so yes, you'll still be able to buy and sell used cars that are powered by combustion engines after 2030, and you'll also be able to buy and sell used hybrids after 2035.

When should I stop buying diesel cars? ›

There's no indication that diesels will become more difficult to run or own in the coming years, and nor is there any proposal for an outright ban apart from the 2030 one on new petrol and diesel car sales. You will still be able to sell your diesel car, and indeed buy and run another used diesel, beyond 2030.

What is the lifespan of a petrol car? ›

In the past, the average lifespan of a car was significantly lower than it is today. Now, you can expect a standard car to last around 12 years or about 200,000 miles. More advanced vehicles like electric cars can go even longer, up to 300,000 miles.

Why are people still buying petrol cars? ›

The main reasons are around convenience. A petrol car will usually be cheaper to buy than a diesel version. You'll save money at the petrol pump, and it's still easier to find somewhere to refuel than hunting for an electric car charging point.

Which fuel lasts longer petrol or diesel? ›

Diesel engines do last longer than petrol ones. Diesel is a light oil and when burned and used as fuel by the vehicle it lubricates the parts of the engine. This prolongs the life of the engine. Petrol is a detergent and washes away oil from the components of the engine, therefore, wearing it out quicker.

Is it worth getting a diesel car? ›

Whether it's worth buying a diesel car in 2022 partly comes down to how you plan to use it. If you're mainly using the car for long journeys on the motorway, then a diesel could make sense. But, if you're just be making short trips across town, then buying a diesel car is unlikely to be the best choice.

What fuel is best for long distance driving? ›

Premium fuel will give better mileage and performance on cars designed or tuned to run on premium fuel.

Can I still drive my diesel car after 2030? ›

Can I still drive my diesel car after 2030? Yes. The ban will only apply to new cars and there are no plans as yet to ban the sale of petrol.

What is better for city driving petrol or diesel? ›

If you do lots of short, low-speed trips, then petrol will be a better option. Diesel engines use a particulate filter to help reduce pollution, but this needs faster runs to keep it in top working condition. If you just do short journeys, it will get clogged and harm a diesel car's running.

Should you drive a diesel car everyday? ›

Need to be driven daily, else maintenance becomes high

Modern diesel cars do not need constant attention. You can use it when you need to. Else you can park it safely without worrying about the parts becoming jammed. Earlier, it was a fact that diesel cars needed to be run more often than petrol vehicles.

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