MOT fail rates by first-use year

1998 Porsche 911 MOT fail rate and common faults

How Porsche 911 cars first used in 1998 did at their MOTs from 2022 to 2023, against all cars of the same age. From 2,201 DVSA MOT tests of these cars. First use is usually the date the car was first registered.

MOT data updated 28 September 2026

At 25 years, tested in 2023

MOT fail rate at age 25 (n=1,073)19.9%

All cars at 25 years (n=313,355)36.3%

Difference−16.4 pts

MOT tests of 1998 cars, 2022 to 20232,201

What stands out

In 2023, at 25 years old, Porsche 911 cars first used in 1998 failed 19.9% of MOTs (1,073 tests), 16.4 points below the 36.3% for all cars that age.
From 2022 to 2023, as these cars went from 24 to 25 years old, the fail rate moved from 20.6% to 19.9%.
The most common fail item that is not a wear item, for the Porsche 911 at 25 years, is catalyst emissions: Lambda reading after 2nd fast idle outside specified limits, at 1.8 per 100 MOTs (all cars: 2.2).

MOT fail rate by test year

Porsche 911 cars first used in 1998: share of MOT tests that failed, by test year, against all cars of the same age. Years with fewer than 1,000 tests are not shown.
Test year	Age	MOT fail rate	Tests (n)	All cars	Difference
2022	24 years	20.6%	1,128	37.8%	−17.2 pts
2023	25 years	19.9%	1,073	36.3%	−16.4 pts

Most common faults at 25 years

These figures cover all Porsche 911 MOTs at 25 years: cars first used 1997 to 2000, tested 2022 to 2025 (n=4,006). The list uses every first-use year so it has enough tests. Wear items (tyres, brake pads, wipers, bulbs) say more about upkeep than about the design.

MOT fail items

Fail item	Per 100 MOTs	All cars
Side/position light not working Wear	2.0	3.4
Catalyst emissions: Lambda reading after 2nd fast idle outside specified limits	1.8	2.2
Rigid brake pipes: excessively corroded	1.5	1.9
Tyre tread below 1.6 mm Wear	1.3	1.4
Headlamp aim: projected beam image is obviously incorrect Wear	1.3	1.8
Dipped headlight not working Wear	1.2	1.3
Headlight aimed too high Wear	1.0	1.3
Brake light not working Wear	1.0	2.6
Wipers not clearing screen Wear	1.0	3.1
Handbrake too weak	1.0	2.3

Per 100 of the MOTs above (n=4,006). A test with two items counts once for each.

Advisories

Advisory	Per 100 MOTs	All cars
Rigid brake pipes: corroded, covered in grease or other material	10.2	14.1
Brake discs: worn, pitted or scored, but not seriously weakened	8.5	8.6
Tyre tread close to the legal limit or worn on the edge Wear	8.4	10.1
Engine oil leaks: leak, but not excessive	8.0	14.9
Tyre condition: slightly damaged/cracking or perishing Wear	4.4	9.1
Registration plate lamp(s): inoperative in the case of multiple lamps or light sources Wear	3.5	3.7
Anti-roll bar link ball joint: slight play	2.7	1.4
Windscreen: damaged but not adversely affecting driver's view	2.3	3.5
Suspension pin or bush worn, without excessive movement	2.3	4.9
Exhaust system: has a minor leak of exhaust gases	2.0	5.3

Per 100 of the MOTs above (n=4,006). A test with two items counts once for each.

Fuel type at 25 years

These figures cover all Porsche 911 MOTs at 25 years: cars first used 1997 to 2000, tested 2022 to 2025 (n=4,006). Each fuel is set against all cars of the same fuel and age. Fuels with fewer than 1,000 tests are not shown.

Fuel	Share of tests	MOT fail rate	Tests (n)	All cars, same fuel	Median mileage
Petrol	100.0%	18.4%	3,952	35.2%	89,073 miles

Fail rate by mileage at 25 years

These figures cover all Porsche 911 MOTs at 25 years: cars first used 1997 to 2000, tested 2022 to 2025 (n=4,006). At 25 years, Porsche 911 cars at 90,000 to 120,000 miles failed more often (21.2%, n=1,244) than those at 60,000 to 90,000 miles (16.4%, n=1,266). Bands with fewer than 1,000 tests are not shown.

Mileage at test	MOT fail rate	Tests (n)	All cars
60,000 to 90,000 miles	16.4%	1,266	35.4%
90,000 to 120,000 miles	21.2%	1,244	38.4%

Car tax rules for a 1998 car

Cars first registered before 1 March 2001 are taxed by engine size: one annual rate for engines up to 1,549cc and a higher rate above that.

These are the rules, not the amount for a specific car. Car tax check

ULEZ and clean air zones

Petrol cars first registered before 2001 usually do not meet Euro 4, so they usually pay the ULEZ daily charge.
The clean air zones in Birmingham and Bristol use the same Euro 4 petrol and Euro 6 diesel standards. The low emission zones in Scotland use them too, but enforce them with fines, not a daily charge.

The Euro standard of the car decides, not the year alone. ULEZ checker

Other years of the Porsche 911

1999 Porsche 911

More on the Porsche 911

Read this with care. A fail rate is not a measure of build quality. How far cars are driven, how they are used and how well owners maintain them all change it, and wear items such as tyres and brake pads are common fails. Compare a model only with cars of the same age. Methodology and limits.

Found one you might buy? Vet the specific car.

These figures describe 1998 Porsche 911 cars as a group, not any one car. The VetTheCar Buying Report looks at the car you are buying: its MOT history, what similar cars did next, and what to ask the seller.

See an example Buying Report All car tools

Source

Contains public sector information licensed under the Open Government Licence v3.0. Source: DVSA anonymised MOT test data, class 4 normal MOT tests, 2022 to 2025. MOT data updated 28 September 2026.

Not affiliated with or endorsed by DVSA. How we calculate these figures · Data sources

Car tax and clean air zone rules are summarised from GOV.UK and Transport for London guidance. They are general rules and are not drawn from the MOT data.