Is it time to give up on diesel? I’ve been crunching the numbers

The price of diesel is soaring, and right now it’s over 30 pence per litre more expensive than petrol, on average. With such a huge price difference, and petrol cars getting more efficient, news editor Jamie Edkins is wondering if there’s any point in buying diesel cars anymore.

When I was a kid, diesel cars were the go-to if you wanted maximum fuel economy. My family had a diesel Peugeot 205, and that car could get a whopping 80mpg on a long run. These days, however, they’re not quite so fuel efficient.

Even the best diesel cars will struggle to top 65mpg, and while that is still more than most petrol cars can get, this does pose a problem.

At the time of writing, the average cost of petrol is 157.2 pence per litre according to Fuel Finder, while diesel is 188.8 pence per litre. And with more than 30 pence between the two, I was wondering if diesel cars are efficient enough to offset the difference.

So I’ve been doing some maths to figure it out, comparing diesel cars with comparable petrol models, as well as hybrid cars. Let’s get into it.

What are the parameters?

I’ve calculated the weekly fuel costs for these cars based on the driver covering 200 miles a week. I’ll also be using the manufacturer’s claimed average fuel economy, and the average cost of fuel at the time of writing.

Keep in mind that fuel prices move up and down by the day, so keep an eye on the latest prices using a service such as Fuel Finder.

Skoda Octavia 2.0-litre diesel vs 1.5-litre petrol

Let’s start with the Skoda Octavia, because the 2.0-litre TDI with 116hp is the most economical diesel car on sale right now. It’ll do 65.7mpg according to official tests.

So to cover our 200 miles, it’ll use 13.8 litres of fuel, and at 188.8 pence per litre that works out to £26.12.

The 1.5-litre mild hybrid petrol is much less fuel efficient, with a claimed economy figure of 56.5mpg. This means it’ll use 16 litres of fuel to do 200 miles, which will cost you £25.30.

That may only be a difference of 82 pence, but it shows that perhaps a diesel car isn’t the money saving hack we once thought it was. The diesel Octavia is also around £400 more expensive to buy than the petrol model.

Peugeot 308 hybrid vs 1.5-litre diesel

Hybrid cars used to be quite a bit more expensive than their petrol and diesel equivalents, but this isn’t the case anymore. The recently-updated Peugeot 308 is available with a 1.2-litre petrol hybrid engine for £27,500, whereas the 1.5-litre diesel is around £700 dearer.

The hybrid will be better for driving around town because it can waft along at low speeds using just the electric motor, making it smoother and more efficient. It’ll return an average of 57.7mpg according to official tests, making it more economical than the diesel. That car will do 56.5mpg.

This means to do 200 miles in the hybrid will cost £24.77, whereas the diesel model will use £38.38 worth of fuel.

So is it time for us to give up on diesel?

If you’re after the lowest running costs, diesel isn’t the safe bet it once was. At least not while prices are this high. I would recommend going for a hybrid car, because not only are they as efficient as diesel cars, if not more, they’re also smoother to drive in town.

That’s not to say these cars don’t have a place though, because diesels tend to produce more torque than petrol or hybrid models, making them better for towing or hauling heavy loads. In a commercial setting, they make a lot of sense.

However, if you’re after the cheapest motoring possible, and have access to off-street parking, you should also consider an electric car. An EV energy tariff could save you a fortune, with some suppliers offering prices as low as seven pence per kWh.

Managing editor Darren Cassey has owned a Cupra Born for around two and a half years, and it averages 4.0 miles per kWh. At 7p/kWh to charge, our 200 miles would cost just £3.50.

In order for a petrol car to be that cheap, it would have to average 408mpg. Some plug-in hybrids may claim to get close to this, but in reality they’ll never achieve that unless you charge them religiously to maximise the EV range. At that point, an electric car will suit most people’s needs.

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