Workshop services

A service is the appointment at which a car is checked rather than repaired. What it covers is set by the manufacturer — by mileage, by time, or by an indicator in the car that factors in how it has been driven. A complete service record is one of the few things a later buyer can genuinely verify.

An oil change is the simplest job on an engine and the one where most can go wrong — not in the workmanship but in the choice of oil. Every manufacturer specifies an approval, and it is not a suggestion: an oil with too much ash will clog a diesel particulate filter, one that is too thin will not hold a film under load.

Not everything that wears on a brake is visible. Pads and discs get thinner, and you notice that — brake fluid, by contrast, draws water out of the air over the years, and every percent lowers its boiling point. On a long descent it can then form vapour in the circuit and the pedal goes to the floor. That is why virtually every manufacturer specifies a change every two years, regardless of mileage.

The tyre is the only connection between car and road, and the contact area is about the size of four palms. In the EU the legal minimum tread depth is 1.6 millimetres — for winter, specialists recommend considerably more, because a winter tyre gets its grip mainly from the sipes in the tread.

An air conditioning system loses refrigerant over the years even when nothing is broken — it is not hermetically sealed, and the seals move. Left undertopped, the compressor runs short of oil, because the oil circulates with the refrigerant. The compressor is the most expensive part of the system, and it fails from lack of refrigerant, not from use.

The timing belt keeps crankshaft and camshaft in step. If it breaks, on most engines the valves meet the pistons and the engine is destroyed — over a part that is replaced on schedule and whose replacement costs a fraction of the damage. The interval is set per engine by the manufacturer, in kilometres and in years; the year limit applies even at low mileage, because the belt goes brittle with time.

A timing chain counts as maintenance-free, and usually that holds. It does stretch over its life, though, and the tensioner only compensates so far. Beyond that the valve timing drifts, the engine runs rough, and the fault memory logs a deviation between camshaft and crankshaft signals — which is the actual evidence, because a noise alone is not a diagnosis.

A clutch is a wear item, but how fast it wears depends almost entirely on how the car is driven — hill starts, towing and riding the pedal cost more lining than high mileage does. So there is no fixed interval. Because the gearbox has to come out anyway, whatever would soon need the same job is usually replaced at the same time.

For years many manufacturers listed automatic transmission fluid as a lifetime fill — meaning the life the manufacturer plans for, not the life the gearbox could reach. Transmission fluid ages under heat and shear, and the clutch packs wear; the debris stays in the fluid. A change at the right time costs far less than a rebuild.

A fault code is a pointer, not a finding. "Oxygen sensor signal implausible" does not mean the sensor is dead — it means the control unit is receiving a signal that does not match the rest. The cause may be an air leak, a broken wire, or indeed the sensor. Read the code and swap the part, and you often swap twice.

An electric car needs less maintenance than a combustion one — no oil, no spark plugs, barely any brake wear because the motor helps slow the car. Other things take their place: the state of the traction battery is the single biggest factor in the car's value, and work on the high-voltage system may only be done by qualified staff.

The starter battery is the part that most often leaves you stranded, almost always on a cold morning. On cars with stop-start it is no longer a simple consumable either: they use AGM or EFB batteries, and many cars need the new battery registered with the energy management system. Without that, it is charged incorrectly and lasts markedly less long.

An exhaust system is more than a pipe: the catalytic converter, the oxygen sensors and, on a diesel, the particulate filter are part of engine management, and a fault there shows up immediately in consumption and power. The particulate filter burns itself clean in use, but only if it gets hot enough — on nothing but short trips that never happens, and over time it clogs.

A misaligned axle does not cost comfort, it costs tyres: even a small toe deviation will scrub the shoulder off a tyre within a few thousand kilometres. The measurement itself is quick — what it reveals is often worn bushes and joints that nobody had noticed.

With body damage there are two separate questions: what you can see, and what is structural. A dent in a door is cosmetic; a bent longitudinal member is a safety matter, because the crumple zone will no longer behave as designed. Only a measurement on a jig says which case you have.

The hard part of a paint job is not the painting but matching the colour. The paint code is on the car — depending on the make in the door frame, under the bonnet or in the boot — but after years in the sun the paint on the car is no longer exactly that shade. Which is why the new paint is blended into the adjacent panels rather than stopped at an edge.

A stone chip in a windscreen can be repaired while it is small, out of the driver's field of view, and has not yet started to crack. It usually cracks not while driving but on a temperature swing — frost overnight, heater in the morning. Put the appointment off for three weeks and you replace the screen instead of repairing it.

Every registered vehicle has to be presented for testing at regular intervals — only the test has a different name in each country, and so do the intervals. What is checked is essentially the same everywhere: brakes, steering, suspension, lighting, tyres, emissions and the body for structural corrosion. Most failures involve lighting and brakes, and both can be checked beforehand.