At a Glance
UK cars have seen 27.6M exhaust problems recorded across 20 years of DVSA MOT data. Microcars over-index on this category by +29% vs the UK average. The category's per-test fail rate has dropped since 2006 — 8.1% → 2.3% (-72% change).
Trend rates normalise failures by UK MOT test volume each year, so a growing number of cars on UK roads doesn't distort the signal. Read our DVSA data analysis methodology →
About Exhaust Problems on UK Cars
The exhaust category covers a major portion of UK MOT failures across cars, vans, and pickups. UK testers have recorded 27.6M exhaust problems across 20 years of DVSA data — patterns useful for buyers checking a used car, owners scheduling preventive repairs, and journalists writing about UK road safety.
Below: which UK car makes most commonly fail MOTs in this category, the specific exhaust problems testers record most often, body-type comparisons, and 20 years of trend data — all drawn from DVSA records, no editorial picks.
UK Car Makes Most Affected by Exhaust
Top 15 UK car makes ranked by exhaust problems recorded in DVSA MOT data
Switch between raw Problem count (Ford, Vauxhall lead because they're bigger fleets), Per-test rate (exhaust problems divided by this make's total MOT tests — normalises for fleet size), and MOT tests (fleet size for context). Hover any bar for all three values plus share of UK exhaust problems.
Most Common Exhaust Problems
The 10 most frequently recorded exhaust problems across all UK makes and models
1.Exhaust system fault
26.5M (60.7%)2.Catalytic converter efficiency low
10.3M (23.6%)3.Spark ignition emissions above threshold
3.3M (7.5%)4.Compression ignition emissions above threshold
1.4M (3.2%)5.Transmission oil leak
1.3M (2.9%)6.Exhaust emissions above threshold (non-catalyst)
453K (1.0%)7.Exhaust leak
254K (0.58%)8.Undertray damaged or missing
106K (0.24%)9.Hydraulic fluid leak
83K (0.19%)10.Exhaust heat shield or sound insulation damaged
34K (0.08%)Exhaust Trend — 20 Years of UK MOT Data
Per-year exhaust failure rate vs the UK all-category average
Each line is the per-year failure rate as a percentage of UK MOT tests. Exhaust rate has dropped from 8.1% (2006) to 2.3% (2024) — a -72% change. Use the filter pills to toggle either line.
Showing all categories. Click a pill to hide; double-click to isolate.
Which Body Type Fails Most on Exhaust?
Per-body-type exhaust problem rate deviation from UK average
A body type that bulges right over-indexes on exhaust per MOT test — structurally more exhaust failures than the UK baseline, not just more problems because it's popular.
Note on body-type classification: each model is assigned a single primary body style. Multi-body models (e.g. Volvo 240, BMW 3-Series, Audi A4, Ford Mondeo) appear under their dominant body — usually saloon — even when they had significant estate or hatchback variants. So the “saloon” bar above includes some genuine estate volume. We're working on per-generation body-type data to fix this.
Tell Us About a Exhaust Problem
Had a exhaust problem with your car? Report it and we'll add it to the database.
Tell Us About a Exhaust Problem
Had a exhaust problem with your car? Report it and we'll add it to the database.
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Frequently Asked Questions
What are the most common exhaust problems on UK cars?
Based on DVSA MOT test records, the top exhaust problems are exhaust system fault, catalytic converter efficiency low, spark ignition emissions above threshold. These three account for 92% of all exhaust failures recorded.
Which UK make has the most exhaust problems?
By absolute volume, Vauxhall has the most exhaust problems recorded (7,173,473 occurrences, 16.3% of all UK exhaust problems) — which partly reflects how many Vauxhall vehicles are on UK roads, not just reliability. See the Most Affected Makes list above for the full ranking.
Which body type fails most on exhaust?
Microcars over-index on exhaust failures by 29% vs the UK average, while SUVs are 49% below average. See the body-type deviation chart above.
Is exhaust getting better or worse over time?
Exhaust failures have improved over the 20-year window — 2006: 8.1% of UK MOT tests → 2024: 2.3% (-72% change). Compare against the UK all-categories line on the chart for context.
How is this data calculated?
DVSA publishes anonymised MOT test records under the Open Government Licence v3. We classify every Reason-for-Rejection (RfR) item into one of 11 DVSA-tested categories, aggregate counts across 20 years of data, and normalise per-year rates by UK MOT test volume so growth in the number of cars on UK roads doesn't distort the trend. Read the full methodology for details.
