MOT advisory guides

These guides take the most common lines on MOT certificates and explain them the way a mechanic would across the bonnet: what the tester saw, whether it's urgent, what the repair usually costs and whether it's a job you can do yourself.

If you've got your MOT result to hand, the quickest route is to paste it into the MOT advisory decoder. It sorts every item by urgency and links to the right guide for each one.

Understanding your MOT result

• What does an MOT advisory mean, and do you have to fix it?. What advisories are, how they differ from minor defects, and whether you have to fix them.
• Can you drive a car that failed its MOT?. When you can and can't drive after a fail, the fines, and how free retests work.
• Nearside and offside: which side of the car is which?. Nearside is left, offside is right. What NSF, OSF, NSR and OSR mean.
• How to check MOT history before buying a used car. Using the free MOT history check to spot neglect, repeat advisories and mileage problems.

Tyres and brakes

• "Tyre worn close to legal limit": what the MOT advisory means. How much tread is left, how long you've got, and why "worn on edge" means tracking.
• Brake pads wearing thin and discs worn: what the MOT advisory means. How long thin pads last, when worn discs fail, and what pads and discs cost.
• Brake pipe corroded MOT advisory: what it means and what to do. How serious rusty brake pipes are, what "covered in grease" means, and replacement costs.
• "Tyre slightly damaged/cracking or perishing": what it means. Harmless surface cracks vs dangerous ones, how to read a tyre's age, and when to replace.

Suspension, rust, leaks and the rest

• "Oil leak, but not excessive": what the MOT advisory means. Where small leaks come from, when a leak fails, and how to track one down.
• Suspension arm bush deteriorated or worn: what the MOT advisory means. What bushes do, when wear turns into a fail, and whether to replace the bush or the arm.
• Anti-roll bar linkage ball joint has slight play: what it means. The knocking drop link: what it is, how urgent it is and how cheap it usually is to fix.
• Exhaust MOT advisories: minor leaks, corrosion and loose mounts. Minor leaks, rusty boxes and tired rubber hangers, plus when the exhaust fails.
• Underside of vehicle generally corroded: MOT rust advisories explained. Surface rust vs structural rust, why some areas matter more, and what to do before winter.
• Windscreen chips and cracks on your MOT: the 10mm and 40mm rules. The zone A rule, the 40mm rule, and when a chip can be repaired instead of replaced.