· UpCars Team · Buying Advice · 7 min read
How to Read MOT Advisories Before Buying a Used Car
MOT advisories are where a used car quietly admits what it's about to cost you. Here's how to tell normal wear from the notes that should send you walking.
Advisories are the small print of a used car’s MOT history — and almost nobody reads them properly. Most buyers scroll to the pass or fail and stop there. That’s a mistake, because advisories are where the car quietly tells you what it’s about to cost you next.
A single “slight play in a suspension arm” on a ten-year-old hatchback is unremarkable. But the same note appearing three years running, or shifting from “slight” to “excessive”, tells a very different story. Learning to read that shift takes about ten minutes of practice, and it can save you anywhere from a few hundred to a few thousand pounds.
What an MOT advisory actually is (and isn’t)
A UK MOT tests roadworthiness and minimum safety standards on the day of the test. It is not a full mechanical inspection. The tester doesn’t assess clutch wear, gearbox condition, turbo health, air conditioning, oil consumption, or whether the cambelt is 20,000 miles overdue.
An advisory is something the tester noticed that wasn’t bad enough to fail the car — but that you, as an owner, should know about. Since May 2018, defects are graded as dangerous, major, minor or advisory. Dangerous and major mean a fail. Advisories are the “keep an eye on this” pile, and the wording itself is where the information lives.
How to find the advisories on GOV.UK
Go to GOV.UK’s “Check the MOT history of a vehicle” service. You’ll need the registration number and the make, or the 11-digit number from a V5C or MOT certificate. It shows every test since 2005, including the mileage recorded at each one, the result, and the full advisory text.
What you’re looking for
- Repeat offenders. The same advisory three or four years running means the owner never fixed it.
- Escalating language. “Slight” becoming “excessive”, or “surface corrosion” becoming “corroded, within 30cm of a suspension mounting”.
- Gaps in the record. A long break between tests, or mileage that goes backwards, needs an explanation.
- One long list. Ten advisories on a single recent test suggests a car being run into the ground.
The advisories that are usually just wear and tear
Some notes are so common they’re almost background noise on older cars. They still matter for negotiation, but they rarely signal a money pit.
Tyres and brakes
“Tyre worn close to the legal limit” is the classic. It means you’ll be buying tyres before the next MOT — budget £60 to £200 each depending on size and brand. “Brake pads wearing thin” or “brake discs worn” is the same story: pads and discs on one axle typically run £150 to £350 fitted. Notes like “tyre has a cut” or “tyre has a nail” can become instant failures, so budget for a replacement.
A tyre advisory two years running on the same wheel often points to an alignment problem, which is another £50 to £120 for a four-wheel alignment.
Slight play in suspension or steering
“Slight play in a track rod end” or “slight play in a suspension arm ball joint” is normal past 80,000 miles. Expect £80 to £250 per corner to replace a worn arm or joint at a good independent garage. A fresh advisory on one corner is a haggling point, not a deal-breaker.
Minor fluid weeps and exhaust corrosion
“Slight oil leak, not excessive” or “exhaust system corroded” turn up endlessly. A weeping rocker cover gasket is a £30 part and an hour’s labour. Surface corrosion on an exhaust back box might last another three years — or you might be replacing it for £150 to £500.
The advisories that come with a bill attached
This is where you slow down and read every word.
Corrosion wording
“Surface corrosion” on a subframe is manageable. “Corroded, within 30cm of a suspension mounting point”, “corrosion to a prescribed area”, or “structural corrosion” is a different world. Welding a sill or floor typically costs £150 to £500 per side, but corrosion around a suspension mount or subframe can mean £500 to £1,500 in fabrication, and sometimes a car that isn’t economical to save.
If you see corrosion advisories on two or more consecutive tests, assume the seller has been putting it off. Ask directly: was it welded, treated, or just wiped with underseal before the test?
Brake pipes and hoses
“Brake pipe corroded” is one of the most common advisory-to-failure escalations in the UK. Hard brake lines corrode quietly, then fail an MOT a year later. A full set of brake pipes is usually £150 to £400 at an independent, more where the pipes run over the fuel tank or subframe. “Brake hose slightly deteriorated” or “cracked” should be treated as urgent — hoses are cheap at £20 to £60 each, but a failure is catastrophic.
Suspension and steering beyond slight
“Slight play” is fine. “Excessive play”, “worn to the point of excessive movement”, or “suspension arm has excessive play” are failures waiting to happen. Leaking shock absorbers are a slow bleed too: £100 to £250 per corner fitted, and they tend to go in pairs.
Emissions and warning lights
“Exhaust emissions close to limit”, “lambda reading outside limits”, or “engine management light illuminated” point to fuelling, sensor or catalytic converter problems. A lambda sensor is £80 to £200 fitted. A catalytic converter is £300 to £900. A diesel particulate filter (DPF) issue can run £800 to £2,000, and if the DPF has been gutted, the car is no longer road-legal and will fail the next test.
Patterns matter more than any single line
One advisory is a snapshot. A sequence is a story. If a car has had “brake pipe corroded” in 2021, 2022 and 2023, the owner has done nothing. If corrosion advisories appear on both rear sills two years running, welding isn’t a maybe — it’s a booking.
Compare the mileage too. A car that recorded 78,000 miles in 2023 and 62,000 in 2024 has either been clocked or has a data error worth walking away from.
Questions to ask the seller
- “This year’s test flagged corrosion on the rear sill — was it welded or just undersealed?”
- “Do you have receipts for the brake pipe replacement, or is it still outstanding?”
- “The advisory says a tyre is close to the limit — has it been replaced since the test?”
- “Can I see the car cold, before it’s been run today?”
- “Is there anything on the MOT history you’d want me to know before I travel?”
Vague answers, or a seller who’s never looked at their own MOT history, tell you plenty.
Walk-away triggers
- Two or more consecutive years of corrosion advisories in a prescribed area.
- “Excessive play” anywhere in the steering or suspension, especially paired with uneven tyre wear.
- A DPF or emissions advisory on a diesel, particularly one with lots of short-journey history.
- Eight or more advisories on a single recent test of a car under ten years old.
- Mileage that drops, test gaps of two years or more, or a seller who won’t let you read the advisories yourself.
Your two-minute pre-purchase checklist
- Pull the MOT history on GOV.UK and screenshot the last four tests.
- Highlight any advisory mentioning corrosion, brake pipes, “excessive”, emissions or DPF.
- Check mileage progression test by test.
- Ask what was done about each highlighted note, and ask for receipts.
- Budget the repair costs into your offer — or walk away if the numbers don’t work.
An MOT pass with a clean history isn’t a guarantee, but an MOT history full of ignored advisories is one of the clearest warnings you’ll get. Read the small print before you fall in love with the car.
When you’re ready to make a change, UpCars.uk is a good place to start — the cars listed there are checked over properly before they go up, so you’re not the one doing all the detective work.
