Petrol vs Diesel: How To Choose | Saga Car Insurance

The UK Government plans to stop selling new petrol and diesel cars in 2035. That’s still a few years away, so you have time to own and enjoy one. But which option is right for you? In this guide, we’ll look at what matters most for car ownership and compare how petrol and diesel perform.

Key takeaways:

Petrol cars are often cheaper upfront, smoother to drive, and have lower repair costs – ideal for short trips and city driving.
Diesel cars offer better fuel efficiency and torque for long-distance or heavy loads, but have higher purchase and maintenance costs.
Consider mileage, budget and environmental impact before deciding.

What’s the difference between petrol and diesel engines?

There are a few differences between petrol and diesel engines:

Petrol engines use spark plugs to ignite the fuel-air mix. They run at lower compression, so they feel smoother and quieter to drive. Petrol engines are lighter, simpler and often cheaper to maintain.
Diesel engines use high compression to ignite fuel without a spark. This makes them more fuel-efficient and better for long-distance driving. They produce more torque, which is great for towing and heavy loads. But they can be noisier and cost more to repair due to extra parts like turbochargers and particulate filters.

Petrol and diesel: the pros and cons

Both fuel types have strengths and weaknesses. Here’s how they compare:

	Petrol	Diesel
Purchase price	Often cheaper upfront	Typically more expensive
Fuel efficiency	Less efficient, especially on motorways	More efficient for long-distance driving
Maintenance costs	Generally lower	Repairs can cost more and take longer
Emissions	Produces more CO₂	Lower CO₂ but higher NOx emissions
Performance	Smoother and quieter	More torque, better for towing

Petrol vs diesel car performance

In the past, diesel engines were labelled as noisy and unrefined, but newer diesels benefit from turbocharging to smooth the performance and noise levels are reduced inside modern cars.

Diesel engines have a powerful fuel injection so are generally more responsive and have better torque than their petrol counterparts, as well as having more pulling power, making them a good choice if you tow a caravan or trailer.

Petrol engines need to be revved to perform well, so they suit a sportier driving style and might be more fun to drive in towns or built-up areas, as well as being more suited to shorter journeys.

Which is more reliable?

Studies show petrol engines tend to be more reliable. Diesel engines work by compressing fuel at very high pressure. This extra strain can lead to more problems over time.

Diesel cars also have a diesel particulate filter. It’s vital for cutting emissions, but it can be costly to replace if it fails.

Repairs for diesel cars can take longer. They can spend more time in the workshop, and parts and labour sometimes cost more.

Petrol vs diesel car pricing and running costs

When deciding between a petrol and a diesel car, it’s worth considering their running costs.

Road tax

Historically, diesel cars attracted higher road tax due to emissions. Since 1 January 2021, all new cars must meet the Euro 6d emissions standard. Diesel cars that meet Euro 6d no longer cost more to tax in their first year compared to petrol cars. However, diesel cars that don't meet Euro 6d standards are subject to a one-band increase in first-year VED rates.

Insurance

When it comes to car insurance, diesel cars often cost more. This is because they typically have a higher purchase price and can be more expensive to repair or replace after an accident or theft.

Emission charges

Diesel engines produce more nitrogen oxides (NOx), which can lead to higher charges in low-emission zones. If you regularly drive in cities with clean air zones, a petrol car may help you avoid extra costs.

Petrol vs diesel fuel consumption

Another consideration for many when choosing between a petrol and a diesel car is fuel efficiency.

Petrol fuel consumption

Petrol engines are generally less fuel-efficient than diesel engines, especially on long motorway journeys. For drivers who mainly make short trips or commute locally, petrol cars are often more practical and cost-effective.

Diesel fuel consumption

Diesel engines excel in fuel efficiency, particularly for high-mileage drivers and motorway travel. If you drive 15,000 miles or more per year, diesel can offer significant savings on fuel costs despite its higher price per litre.

Learn how to work out your mileage with our annual mileage calculator.

Is diesel cheaper than petrol to buy and run?

Diesel cars are known for having better fuel economy, especially when it comes to motorway driving. Diesel currently costs more than petrol at the pump but looking at diesel vs petrol fuel price over time, diesel works out cheaper because of its lower fuel consumption.

If you drive over 15,000 miles a year, mostly on motorways, from a fuel efficiency point of view driving a diesel car makes sense. But if most of your journeys are local trips to the shops or a short commute, a petrol engine will almost always be a better option.

Diesel cars previously had higher car tax to pay compared to petrol cars, but since 1 January 2021 all new cars must comply to the emissions standard Euro 6d, which means diesel cars will no longer cost more to tax in their first year.

When it comes to longevity, diesel does last longer than petrol, as diesel fuel can prolong the life of an engine compared to petrol engines. But diesel engines can cost more to repair due to their complexity and need for regular engine filter changes.

And when it comes to insurance, diesel cars may cost more to insure, due to their higher initial cost and also the costs to repair or replace them after accident or theft.

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