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Porsche 911 vs Porsche 959: reliability comparison

MOT pass rates, common faults and mileage compared from real UK MOT data.

Porsche 911
85%
MOT pass rate · 74,656 vehicles
Porsche 959
92%
MOT pass rate · 31 vehicles
Verdict: On MOT pass rate the Porsche 911 (85%) and Porsche 959 (92%) are very close — weigh the individual measures below, and remember condition depends on age, mileage and upkeep.

Head to head

Measure Porsche 911 Porsche 959
MOT pass rate 85% 92% ✓
MOT failure rate 15% 8% ✓
Faults & advisories per test 1.1 0.4 ✓
Dangerous-fault share 1% ✓ 4%
Average mileage 70,982 mi 23,089 mi
Sample size (vehicles) 74,656 31

Most common faults

Porsche 911

  1. Nearside Rear Tyre worn close to the legal limit (4.1.E.1)
  2. Offside Rear Tyre worn close to the legal limit (4.1.E.1)
  3. Under-trays fitted obscuring some underside components
  4. Nearside Front Tyre worn close to the legal limit (4.1.E.1)
  5. Offside Front Tyre worn close to the legal limit (4.1.E.1)
  6. Oil leak, but not excessive (8.4.1 (a) (i))

Porsche 959

  1. Offside Rear Tyre worn close to the legal limit (4.1.E.1)
  2. Nearside Rear Tyre worn close to the legal limit (4.1.E.1)
  3. Offside Front Tyre worn close to the legal limit (4.1.E.1)
  4. Nearside Front Tyre worn close to the legal limit (4.1.E.1)
  5. Oil leak
  6. Nearside Windscreen washer provides insufficient washer liquid (8.2.3)

Reliability FAQ

On MOT pass rate the Porsche 911 (85%) and Porsche 959 (92%) are very close — weigh the individual measures below, and remember condition depends on age, mileage and upkeep.

Full Porsche 911 report Full Porsche 959 report Most reliable cars

Pass rates are computed over completed (pass/fail) MOT tests. Reliability also depends on age, mileage and upkeep — see each model's page for the full picture.