Guide to buying a second-hand diesel car
Buying a second-hand diesel car is different to buying a petrol car, as they are initially more
expensive and their complex engines come with a different array of problems that, if not spotted,
could cost you a lot of money later on. This guide looks at the challenges of buying a second-hand
diesel car, and gives you the basic tools to spot any potential problems.
Saving money with a diesel engine
Most people are aware that diesel cars run with much better fuel economy than petrol cars. But
diesel is more expensive, so the savings aren’t as straightforward as they first seem. Diesel also
produces less carbon emissions than petrol, so the car tax is cheaper. However, it may take a while
to notice these savings, as diesel cars, used or brand-new, are more expensive than equivalent
Unless you’re driving more than 20,000 miles, it’s unlikely that you’ll feel the financial benefit of
driving a diesel car in the first year — or even the second year. If you’d like to find out more about
the economics, this Confused.com article goes into a lot of detail about the differences in costs over
the first few years of owning a petrol and diesel car.
Prices are a little different with second-hand cars, as petrol cars tend to depreciate in value faster
than diesel cars. So what does this mean? It means that a diesel car, new or second hand, is going to
be more expensive initially, and drivers will only save money if they drive their second-hand diesel
car for a few years. This means that choosing your car is a big decision, as you’re going to be driving
it for quite a while.
What to look out for when buying a second-hand diesel car
Diesel engines are complex, sturdy and reliable. However, should something go wrong with a diesel
engine, it is much more expensive to repair than a petrol engine. For this reason, you should be very
particular when selecting your second-hand car. Take it for a test drive, or at least start it up and
listen to its engine. If the engine doesn’t sound right, ask the seller about it. Here are some more
things to look out for with a diesel engine:
Rough running: If the engine sounds gravelly and very loud it could just mean that there’s very little
fuel in the tank. But an engine running rough can also be an indication of bigger problems, such as a
blocked fuel supply or a faulty fuel injector.
Misfiring: If the engine sounds like it is misfiring, then there may be a problem with the fuel injector.
Poor starting: Watch out for an engine that is hard to start, as this can indicate a whole host of
problems, such as faulty glow plugs, faulty fuel injectors and larger internal engine problems.
Excessive exhaust smoke: Diesel exhaust smoke can be white, black or blue, and the different types
of smoke can indicate different problems with the engine.
Check the battery condition in the engine bay, does the car turn over and start quickly? Does it struggle? On a cold morning the car will be harder to start and put more strain on the battery, in which case you may need to purchase a new car battery, although they are not expensive.
This diesel troubleshooting resource from United Diesel outlines the differences between the various smokes and it covers other problems as well.
You should be sceptical if someone tells you that any faults will be cheap to fix. This is never the case
with diesel cars. Some problems with diesel engines can also be really tricky to diagnose, so you may
not notice a problem until you’ve already made your purchase, and the seller might not even know
there is a problem in the first place. It’s for this reason that it’s always preferable to buy a second-
hand diesel car from an established used-car vender. Companies like We Buys Car For More have
mechanics that check all of the cars they buy and sell. This makes it an easier, risk-free way for
customers to buy second-hand diesel cars.
Whichever car you’re look for, staying informed throughout the buying process is absolutely key to
ensuring you get value for money. Ask a lot of questions and refer to this guide whenever you need