Is a diesel still better than petrol for high mileages?

I have been a diesel car driver covering around 30,000 per year for the last 10 years and would like to add my two pence to the conversation.

Along the A1, the cheapest fuel I have found is at Tesco Huntington, with petrol at £165 and diesel at £183.

Comparing a BMW F30 320d and 320i M Sport Auto using an online tool, I think the petrol is a better option even at 25,000 miles per year.

According to the website, I will get 50.2mpg from diesel and 38mpg from petrol. At 25,000 miles per year, diesel is £4,475, and petrol is £4,900. I agree that the petrol version will cost an additional £425 per year. However, with the purchasing price difference of about £2,000, the breakeven point will be at year four. Calculating the additional cost of higher insurance, servicing, and AdBlue for the diesel car will equate to a breakeven point at year five.

As you might have noticed, I have not included DPF in my costing for the diesel or usage of E10 petrol in my costings.

How can Honest John continue to recommend diesel below 30,000 miles per year?

Asked on 1 November 2022 by SH

Answered by Andrew Brady
Our Real MPG data suggests readers see 51.4mpg on average from the 320d and 33.1mpg from the 320i. If you're covering 25,000 a year at 166.54p/litre (the average petrol price this week according to the RAC's Fuel Watch) in the 320i, you'll pay £5718.32 a year in fuel. If you're covering 25k a year at 190.49p/litre (diesel) at 51.4mpg, you'll pay £4211.99 in fuel. That's quite a significant saving of more than £1,500 every year.

Running costs aside, diesels are generally better suited to long-distance driving than petrols. They have more low-down torque which makes them more relaxed on motorway drives. They have a longer range, so you'll have to stop and refuel less often. And, if you're covering 25,000-plus a year on the motorway, you're unlikely to have issues with the DPF as it'll regenerate regularly and not get clogged up.
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