Reading the service book: what the stamps tell you

A stamp in the service book says: on this date, at this mileage, this business opened a job under the manufacturer's maintenance schedule. It does not say which parts were replaced, whether a recommended job was declined, or whether the workshop noted faults the customer then chose to leave. That information is on the invoice, not in the book.

That is why asking for the invoices is not pedantry but the real question. A book with an unbroken run of stamps and not a single invoice is worth less than a book with two stamps missing and a folder full of receipts. The folder shows what was actually done to the car; the book only shows that somebody turned up.

Invoices read quickly once you know what you are looking at: the date, the mileage, the line items with part numbers, and the note about declined work. That last point is the most valuable. A line reading “rear discs worn, customer declines” on the service before last tells you more about the car and about its keeper than any stamp does.

Every entry carries a date, a mileage and a business. More can be derived from those three figures than most buyers use. Write the entries out one below the other and work out the intervals: how many kilometres and how many months lie between each pair of appointments?

The mileage curve must rise and must not step backwards — that is the familiar test. The intervals in months are less familiar and at least as revealing. A car that went to a workshop twice a year for years and then not at all for three was either barely driven in that time or looked after somewhere else. Both have an explanation, and the seller should know which.

The name of the business is the third trail. If it changes now and then that means nothing bad; a keeper moves house or finds somewhere cheaper. If it changes at every appointment, and the businesses are far apart, it is worth asking which region the car actually lived in — for corrosion that makes a difference.

Manufacturers either prescribe servicing at fixed intervals — by distance or by time, whichever comes first — or they let the car work it out. In the second case an algorithm derives the next appointment from the driving profile, oil ageing, the proportion of cold starts and the engine speed distribution, and displays it in the instrument cluster. Both approaches are fine, but they produce very different books.

With variable intervals, apparently impossible gaps can appear between entries. That is not a warning sign as long as the car has mostly covered long distances. It is one if the same car was used in town on short trips: then the intervals will have run too long, and the oil ended up carrying fuel dilution rather than doing much lubricating.

So look at the oil specification on the invoice as well. Modern engines with a particulate filter require low-ash oils to a specific approval; a cheap oil of the wrong specification loads the filter faster, and what was saved at the counter is paid for in the workshop. The approval appears as a code on the invoice, and the business will tell you over the phone.

The most expensive maintenance items are rarely part of the regular service but separate jobs with their own intervals. Looking only at the stamps means missing exactly the work whose omission costs real money. Ask about each of these points, whether and when it was done, and ask to see the invoice.

One rule of thumb helps with priorities: the items that fall due by time are the ones most often overlooked on low-mileage cars, because the odometer looks reassuringly small. Cambelt, brake fluid and coolant age just as much standing still as in motion, and their failure does not depend on how far the car has travelled.

Several manufacturers have kept service histories centrally rather than on paper for years now. The workshop enters the service into the maker's system against the chassis number; a printed book is then either absent or empty, even though the history is complete. On such cars the absence of a book is not a defect but the norm.

A printout from that system is the best document available: it does not come from the seller, it is tied to the chassis number, and it cannot be produced with a rubber stamp. Any franchised workshop for the make can generate it; the keeper's consent is normally required. A seller who is serious about selling will get hold of it.

On a car serviced by independent workshops, the maker's system holds little or nothing — that too is not a defect but a consequence of where it was serviced. Then the invoices matter again. What counts is knowing which of the two cases you are in before drawing a conclusion from an empty book.

A gap is at first only a gap. Common and harmless reasons: the car stood for a year, it was looked after in that period by a business that does not stamp books, or the keeper changed the oil himself — not unusual on older cars. Unexplained gaps are a different matter, and they belong in the price negotiation.

Where a book is forged it is almost always forged together with the mileage, and usually badly. The signs are quickly listed: every stamp in the same colour and at the same angle, identical handwriting across several years, a stamp with no address or phone number, a business that does not exist or never handled the make, and a book that looks as though it never lived in a glovebox.

The most effective test costs one phone call. Ring one of the listed businesses, give the chassis number and ask whether the car was ever worked on there. A workshop will not give you details for data protection reasons, but whether a number exists in their system is something they will usually confirm. A no at that point ends the appointment, not the negotiation.

For the substance of the car it makes no difference who did the servicing, as long as it was done to specification with the right parts and fluids. For the price it does: an unbroken history with the franchised network is worth more on the market, particularly on younger cars, and it is a condition of some manufacturer warranty programmes.

The difference also matters for goodwill. A manufacturer contributing to a repair beyond the warranty will look at the history in its own system. If it is not there, the legal claim is no smaller — there never was one — but the chance of a contribution is.

On a car much past seven years old this barely matters any more. By then all that counts is whether the work was done, and an independent workshop with invoices and part numbers documents it just as well as a stamp.

A car with no documented servicing is not unsellable, just to be valued differently: you buy it on the assumption that the time-based items are due. That can be quantified — before the appointment, get a quote for a cambelt, brake fluid, transmission oil and a full service on that engine, and negotiate with that figure rather than with an impression.

After the purchase the history starts with you. The sensible route is a baseline service in the first weeks, renewing every fluid whose age is unknown, plus a written assessment of the brakes, suspension and exhaust. It costs once and puts an end to the guesswork.