MOT Failure Rates by Car Age: When Do Cars Start Failing?

Every car that stays on UK roads long enough will eventually start failing its MOT more frequently. The question is not whether your vehicle's MOT failure rate by age will increase, but when, by how much, and for what reasons. DVSA open data covering tens of millions of annual tests gives us an unusually precise answer — and the results have important implications for used car buyers, owners deciding whether to repair or sell, and anyone trying to predict future ownership costs.

The First MOT: Year Three

New cars in the UK are exempt from the MOT for their first three years. When a vehicle reaches its first test, the pass rate is very high — typically around 88–91% across the fleet, depending on the year and model mix. Most new cars are covered by manufacturer warranty during this period, encouraging owners to report and fix faults promptly. Servicing is often carried out by franchised dealers who flag developing issues before they become failures.

The primary failure categories at the three-year test are lighting (blown bulbs or failed LED units), tyres (pressure or minor wear), and in rarer cases electrical system faults triggered by warning lights. Structural, mechanical, or brake failures at this age are rare and usually indicate either manufacturing defects or accident damage that has not been properly repaired.

Years Four to Six: The Honeymoon Period Ends

Between the ages of four and six years, MOT first-time pass rates decline gradually from the early-90s percentage range to approximately 80–83%. The types of failure shift noticeably during this period:

• Tyre wear: Vehicles now past their original tyre set lifespan, and with owners varying significantly in how proactively they replace tyres, tread depth failures increase.
• Brake pad wear: Front brake pads on a typical family car last 30,000–50,000 miles. By year five to six, many vehicles are approaching their second or third set and owners who service infrequently may have missed the warning wear indicators.
• Wiper blades and minor lighting: These consumable items are replaced less consistently than tyres and brakes and become increasingly common advisory and minor failure causes from year four onwards.

The four-to-six year window is also when warranty coverage typically lapses on most mainstream brands, and owner servicing discipline often decreases as a result. This is reflected directly in MOT failure rates by age — the loss of warranty is visible as a small but measurable uptick in failures from year four.

Years Seven to Ten: The Risk Curve Steepens

The most significant increase in MOT failure rates occurs between years seven and ten. First-time pass rates drop to approximately 70–75% across the fleet during this period. This is not primarily driven by wear items like tyres and brakes — those are ongoing — but by the emergence of age-dependent deterioration:

• Corrosion of brake pipes and fuel lines: Steel brake lines typically last seven to twelve years in UK conditions before corrosion reaches a point where surface pitting or perforation creates an MOT failure. The failure rate for this item increases steeply from year seven in models without comprehensive underbody protection.
• Suspension bush and ball joint wear: Rubber suspension bushes degrade with age as much as with mileage. By year eight, most vehicles will show some suspension play that triggers an MOT advisory — and many will fail outright if the play exceeds limits.
• Exhaust system integrity: Exhaust components corrode from the inside out through condensate accumulation and from outside through road salt exposure. Perforated boxes or cracked downpipes generating emissions failures become increasingly common from year seven.
• Engine management and emissions: Failed lambda sensors, EGR valve issues, and catalyst deterioration cause emissions failures to rise sharply from year eight in many models, particularly diesels whose DPF systems begin to reach end-of-life.

Years Ten to Fifteen: High Failure Territory

Vehicles aged ten to fifteen years record first-time MOT pass rates of approximately 60–68% across the overall UK fleet. This is the age bracket where corrosion-related structural failures — previously rare — begin to appear with meaningful frequency. MOT examiners assess structural corrosion at prescribed check points around seat belt mountings, suspension strut top mounts, and subframe mounting points. Perforation within 30 cm of these areas is a major defect that fails the test.

The categories driving elevated failure rates in the ten-to-fifteen age bracket include:

• Body and structural corrosion: Models without factory rustproofing or comprehensive underseal are increasingly vulnerable from year ten. UK road salt use — approximately 1.8 million tonnes spread annually — is significantly more aggressive than in many European countries, meaning UK-operated vehicles age faster structurally than the same models operated in southern Europe.
• Steering rack wear: Electric power steering systems introduced from the mid-2000s show increasing failure rates from year ten, primarily through motor or sensor failures rather than mechanical wear. Hydraulic rack failure is less common but still present in this age bracket.
• Cam belt failures: Vehicles in this age bracket that have not had cam belt replacements at the correct interval — often missed by owners who are unaware it's due or deterred by the cost — may appear at MOT with a belt close to or beyond its safe service life. While the MOT doesn't directly check belt condition, a belt failure during the test or shortly after represents a serious engine damage risk.

Check a vehicle's full advisory history before this type of structural corrosion becomes an MOT failure. Our MOT history check shows every advisory recorded against a registration, including corrosion-related notes that indicate the vehicle's structural condition trend over time.

Beyond Fifteen Years: Veteran Vehicle Challenges

Vehicles aged fifteen or more years make up a declining but still significant portion of the UK MOT-tested fleet. First-time pass rates for this group fall below 60% in many categories, but the picture is more nuanced than the headline figure suggests. Vehicles that have survived in roadworthy condition to this age tend to be either well-maintained examples kept by enthusiasts and careful owners, or low-mileage vehicles that have been cossetted throughout their life.

The failures in this category are heavily skewed toward corrosion and age-related rubber degradation — steering rack gaiters, suspension boot splits, and body corrosion — rather than wear items. A fifteen-year-old vehicle with consistently good service history and regular waxoyl or equivalent underbody treatment can record pass rates comparable to a ten-year-old neglected vehicle, demonstrating the outsized impact of maintenance quality on MOT failure rates by age.

What This Means for Owners and Buyers

The MOT failure rate by age curve has direct financial implications. A vehicle entering the seven-to-ten year risk window should be evaluated differently from one in the four-to-six year honeymoon period — not just in terms of purchase price but in terms of realistic annual maintenance budget.

For existing owners approaching the higher-risk age bands, the most effective strategy is to review the vehicle's MOT advisory history systematically and address accumulating advisories before they become failures. A brake pipe advisory noted at year seven is a strong signal that replacement should be scheduled before year nine. Use our free car check to pull up the full history and identify any developing patterns.

For buyers, understanding the age-related failure curve should influence negotiation strategy. A ten-year-old vehicle with multiple previous brake and suspension advisories is likely to require several hundred pounds of remedial work in the near term — that cost should be reflected in the purchase price. Our common MOT failures guide explains what each advisory category typically costs to rectify, giving you the data you need to negotiate. And if you want to know exactly where your current vehicle sits in its MOT life cycle, a quick MOT check will show you the test expiry date and the full pass and advisory record from the most recent test.