MOT advisories, translated: which ones mean fix it now.

What an advisory actually means

An MOT advisory is a note that something is approaching the boundary of acceptability without yet crossing it. The car has passed. But it is on the record, and the expectation is that you will monitor or address the item.

The problem is that advisories vary enormously in urgency. A tyre at 2mm of tread is different from a brake pipe with surface corrosion. A worn drop link is different from an oil leak dripping onto an exhaust. The certificate gives you the text; it does not tell you the timeline.

Here is what each common advisory category means for how quickly to act.

Tyres near the limit (tread approaching 1.6mm)

The legal minimum tread depth is 1.6mm across the central three-quarters of the tyre's width. An advisory here means the tester measured a point that is close to that limit.

The urgency depends on the actual reading. A tyre at 2mm in one spot has months of normal use left. A tyre at 1.7mm measured across multiple points needs planning within a few weeks. The key consideration is not just the tread remaining, but how quickly the specific car wears its tyres. A heavier car on sticky tyres will drop 0.3mm of tread faster than a lighter car on touring rubber.

Plan the replacement rather than rushing it, unless the reading is very close to the limit. When you do replace, check whether the wear pattern is even. Uneven wear indicates a wheel alignment or suspension issue; fitting new tyres without addressing the root cause means they will wear unevenly too.

Suspension components with play (ball joints, drop links, wishbone bushes)

This category is more serious than tyres and deserves prompt attention.

Play in a ball joint or a wishbone indicates wear beyond design tolerance. The component still works, but its remaining life is shorter than the measurement implies. Joint degradation is not linear: it is gradual for a long time, then accelerates as the wear surface area reduces. A ball joint that passed with a minor advisory can fail before the next annual inspection.

Drop links are less critical than ball joints but still worth addressing. A worn drop link allows the anti-roll bar to operate imprecisely, which changes the car's cornering behaviour.

If you have been told about suspension play, the question to ask is which component and how much play. A small amount of bush deflection is normal. Movement in a load-bearing ball joint is not. We will give you a straight answer about the timeline when you bring the advisories to us.

Brake pads and discs near worn

Brake advisories on pads and discs are timing items, not emergency items, unless the reading is extremely close to the minimum.

Most pad advisories suggest the friction material is at 2 to 3mm. The legal minimum is 1.5mm, and most quality pads have a wear indicator that contacts the disc around 2mm. So you have some time. The important point is to plan the replacement in advance and not to defer it until the wear indicator squeals in traffic.

If the advisory specifies disc wear as well as pad wear, look at the rotor measurement compared to the discard thickness. Discs that have reached their minimum thickness cannot be machined down and must be replaced. The tell for rotor wear is a visible lip around the edge of the disc where the swept area meets the unswept rim. If that lip is significant, the discs are on their way out whether or not the advisory flags it explicitly. If you have pedal vibration under braking as well, mention it when you book — that points to warping, which the static MOT test cannot detect.

Corrosion: non-structural versus prescribed area

Corrosion advisories are the ones that require the most interpretation.

Surface corrosion on the body, sills, or wheel arches is cosmetic. It does not affect the structural integrity of the car and will not cause an MOT failure unless it progresses to penetrate the chassis or structural sections.

Corrosion in a "prescribed area" is different. The MOT inspection has defined zones around steering, suspension mountings, brake lines, and sub-frame attachment points where corrosion affects safety-critical systems. An advisory noting corrosion near these areas means the tester saw something close to failing but not yet failing. These items move to the urgent category. A tester who sees light corrosion on a sub-frame mount today may see the same mount fail next year, and the consequences of a suspension pickup point failing are severe.

If your advisory mentions corrosion near any brake line, steering component mounting, or suspension pickup point, ask specifically for the location and get it inspected by an independent mechanic before the next MOT.

CV boot splits (without grease loss)

A split CV boot is cheap to fix and genuinely expensive to ignore.

The boot keeps grease in and contamination out. When it splits, grease escapes with each cycle of the joint while water and grit work their way in. The joint continues to function until the grease is gone and the contamination has established itself, at which point wear accelerates rapidly. A boot replacement costs a modest amount. A CV joint replacement after the boot has been ignored costs significantly more.

Act on CV boot splits within a few weeks of the advisory.

Oil leaks, fuel leaks, brake fluid leaks

These are always investigate immediately, always sooner rather than later.

Oil leaks vary from slow seeps from an ageing rocker cover gasket to active drips from a failing oil filter housing. The advisory tells you it was observed, not how serious it is. Oil dripping onto an exhaust or turbo is a fire risk; oil contaminating brake components is a braking risk. Even a slow seep can worsen.

Brake fluid leaks are the most urgent. A brake fluid leak is directly on the path to brake failure. Investigate the same week, not at the next service.

Bringing advisories to us

If you have a certificate full of advisories and you want an honest read of what to do first, bring it in. We will go through each item, tell you what the timeline looks like, and give you a prioritised list. No upsell. No scare tactics. The jobs that need doing now will be the ones we tell you need doing now.

You can also use our MOT service page to start a quote, or talk through what is on the certificate before you commit to anything.