How to read a service history before you buy a used car

A service history is the closest thing a used car has to a medical record. It will not tell you everything, but read carefully it reveals how the car has been treated and what is likely to come next. Here is how to go through one without being an expert.

What a good history looks like

A good history is regular, dated and consistent. Each entry has a date, a mileage and a description of what was done, ideally backed by an invoice from a named garage. The mileage goes up steadily between entries, and the gaps between services roughly match what the manufacturer recommends for that car.

It doesn't have to come from a main dealer. A well-documented history from a reputable independent garage can be just as reassuring.

Check that the mileage makes sense

Line up every record that mentions mileage: service invoices, inspection certificates and tyre receipts. The numbers should always increase. A reading that goes down, or a long period with almost no change, deserves a question.

Compare the mileage with the car's age. Very low or very high yearly mileage isn't automatically bad, but it should fit the seller's story about how the car was used.

Look for the big scheduled jobs

Some jobs are expensive and only happen every few years, such as a timing belt replacement, gearbox oil change or major brake work. Find out from the owner's manual or a garage when these are due for this model, then check whether the history shows them.

If a big job is due soon and there is no record of it, factor the cost into your offer.

Red flags

None of these automatically rules a car out, but each one is a reason to ask more questions or get an independent inspection.

Long unexplained gaps between services.
Stamps in a service book with no invoices behind them.
Repeated repairs to the same system.
Records that stop suddenly a short time before the sale.
A seller who can't explain entries or gets defensive about them.

Questions to ask the seller

Why are you selling the car?
Has it had any accidents or major repairs?
When was the last service, and what's due next?
Are there any warning lights or known faults?
Can I take it to a garage for an inspection before buying?

Keep your own history from day one

Once you buy, start your own record straight away. Car Ahead lets you log each service with its date, mileage and cost, and uses that history to estimate what's due next. A clear record also helps you when it's your turn to sell.

This guide is general information, not professional advice. Car Ahead's estimates are calculated from the data you enter and can't replace an inspection by a qualified mechanic.