Glossary
Car servicing and MOT words, in plain English
Garages use these words as if everyone knows them. Here is what each one actually means, what it costs you if you ignore it, and where it turns up on a quote or an MOT certificate. 29 terms, written by James Snow.
MOT words
The words on an MOT certificate are defined by the DVSA, not by the garage, and they mean specific things. These are the ones people ring us about.
- MOT
An MOT is the annual roadworthiness test a car in Great Britain needs once it is three years old. It checks safety and emissions items against the DVSA inspection manual on the day of the test.
An MOT is not a service. It tells you whether the car is legal to drive, not whether anything is about to wear out.
- Advisory
An advisory is something the tester noticed that is not bad enough to fail the car. The car passes, and the advisory is printed on the pass certificate as a warning that the item is heading towards a failure.
An advisory is a job you can plan for rather than one you have to do today. Most of them get forgotten until the following year.
- Minor defect
A minor defect is a fault that does not affect the car's safety or the environment enough to fail it. Like an advisory, the car passes and the defect is printed on the certificate.
- Major defect
A major defect fails the MOT. The car is not legal to drive on the road until the fault is repaired and the car passes a retest.
- Dangerous defect
A dangerous defect fails the MOT and means the tester judged the fault to be an immediate risk to road safety. The car should not be driven away at all until it is fixed.
Tyres and brakes are what testers mark dangerous most often.
- PRS, pass after rectification
PRS means the car was in a failing state when it was tested, the fault was repaired within an hour at the test centre, and it then passed. The certificate records it as a pass.
It matters if you are comparing failure rates, because a PRS car did arrive in a failing state.
- Retest
A retest is the second test after a car has failed and been repaired. It re-examines the items that failed rather than testing the whole car again.
Servicing words
Garages use these words differently from each other, which is half the confusion. Here is what we mean by them, and what you actually get.
- Interim service
An interim service is the smaller of the two routine services. On our price list that is the engine oil, the oil filter and the air filter, plus a safety check. It suits cars doing higher mileage that need attention between full services.
- Full service
A full service covers the interim work plus a cabin filter, a coolant flush and a fuller system check. For most cars it is the once-a-year job.
- Major service
A major service is the most thorough of the three. It adds the fuel filter, a brake fluid change and a brake inspection on top of the full service.
- Service interval
A service interval is how often the manufacturer says a car should be serviced, given as a mileage, a time, or whichever comes first. It varies by make, model and engine.
- Health check
A health check is an inspection with no work included. We look over the car against a fixed list, score each item, and tell you what we found and what it would cost to put right.
Nothing is replaced or adjusted as part of a health check. It is a report, not a repair.
- Labour only
Every price published on this site is labour only. Parts are quoted separately per car, because the same job needs different parts at different prices depending on the make, model and the quality of part you choose.
- Call-out
The call-out is the fixed charge for coming to you rather than you bringing the car to a garage. It is charged on every visit and it is shown separately from the labour price, never hidden inside it.
- Diagnostic
A diagnostic is plugging proper equipment into the car to read stored fault codes and live data, then working out what the codes actually mean. It is charged separately from the call-out.
If you go ahead with the repair, the diagnostic charge comes off the price of that repair. The call-out does not.
Parts and warning lights
The parts that come up most often in a quote, and the lights that make people ring a mechanic.
- Brake pads
Brake pads are the friction material that presses against the brake disc to slow the car. They wear down every time you brake and are designed to be replaced.
Worn pads are one of the most common things an MOT tester notes, and it is usually an advisory before it becomes a failure.
- Brake discs
Brake discs are the metal discs the pads clamp onto. They wear more slowly than pads, but they wear, and they can warp or corrode.
Discs and pads are usually replaced together per axle, because new pads on a worn disc will not bed in properly.
- Brake fluid
Brake fluid is the hydraulic fluid that carries the pressure from the pedal to the brakes. It absorbs water from the air over time, which lowers its boiling point and makes the pedal feel soft under heavy braking.
That is why it is changed on time rather than when it looks dirty.
- Engine management light
The engine management light, sometimes called the check engine light or the MIL, means the car's computer has stored a fault code about the engine or emissions system. It does not tell you what is wrong on its own.
Steady usually means get it looked at soon. Flashing usually means stop driving.
- OBD port
The OBD port is the standard socket a mechanic plugs diagnostic equipment into, normally under the dashboard on the driver's side. OBD stands for on-board diagnostics.
- Alternator
The alternator charges the battery and runs the car's electrics while the engine is running. If it fails, the car will run on the battery alone until the battery is flat.
- Starter motor
The starter motor is the electric motor that turns the engine over so it can start. A failing one often sounds like a single click, or a whirr with no engine turning.
- Clutch
The clutch connects and disconnects the engine from the gearbox in a manual car so you can change gear. It is a wearing part and a slipping clutch is the usual sign it is near the end.
- Coolant, or antifreeze
Coolant is the liquid that carries heat away from the engine to the radiator. It also stops the system freezing in winter and contains corrosion inhibitors that wear out over time.
- Oil grade
An oil grade such as 5W-30 describes how the oil flows when cold and when hot. The right grade for a car is set by the manufacturer, and using the wrong one can affect the engine and, on some cars, the emissions system.
Words for work we do not take on
People ask us what these mean, so they are here. We do not do any of them, and we will say so and point you somewhere that does rather than have a go.
- Cambelt, or timing belt
A cambelt keeps the engine's valves and pistons moving in step. It is replaced on a schedule rather than when it fails, because if it snaps the engine is usually damaged beyond economical repair.
We do not replace cambelts. If yours is due, it is a job for a workshop.
- DPF, diesel particulate filter
A DPF traps soot from a diesel exhaust and periodically burns it off at high temperature. Short journeys stop that happening, which is how a DPF gets blocked.
We can read a DPF fault and tell you what it says. We do not carry out DPF cleaning.
- EGR valve
The EGR valve feeds a measured amount of exhaust gas back into the engine to lower combustion temperature and reduce emissions. It can clog with soot and stick.
We do not carry out EGR cleaning.
- Automatic and DSG gearboxes
DSG is a type of automatic gearbox using two clutches. Automatic and DSG boxes are sensitive to the exact fluid and filling method used.
We do not work on automatic or DSG gearboxes. The wrong fluid or method can cause expensive damage, so those go to a transmission specialist.
Still not sure what you have been quoted for?
Send us the quote or the MOT certificate and we will tell you plainly what it says. No obligation, and we will say so if the work does not need doing.