What Car? Q&A - Are diesels better for high-mileage?

Q: Why do dealers recommend diesel engines for high-mileage drivers? Does a bigger engine mean it’s longer lasting? How long do they typically last?
Richard Hemingway

A: The more miles you do the more sense a diesel makes because of the greater economy it offers. You’ll fill up less often and, despite the fact diesel costs more at the pump, you'll eventually pay off the extra money the car probably cost to buy and start to save money.

A low mileage user might never recover this premium, however. A Ford Focus diesel, for instance, can cost £1500 more than a petrol – a price premium that can take many thousands of miles to recover.

How long an engine lasts depends on how stressed it’s been through its life (how hard it’s been worked by the driver) and how well it’s been taken care of (so regular maintenance, good oils and limited cold starts will all help).

So, a larger engine would be able to provide the same performance as a smaller engine with less stress and less load, potentially lasting longer as a result. If you’re buying second-hand it would be pretty difficult to find out if this had been the case!

A diesel also operates at these less stressful parts of the rev range and can also be longer-lasting as a result.

All in all, engine life varies dramatically, however, and is subject to too many variables to say how much longer a larger engine, or a diesel, might last.

In many cases, the engine will easily outlast the rest of the car.