How reliable is the Porsche 928 compared with other cars?

We do not publish a comparison for the Porsche 928, because the cars of this model that have been tested do not cover a wide enough range of ages and mileages. Its raw pass rate is 81.1% across 650 tests, but comparing a raw rate between models mostly ranks them by how new they are rather than how good they are. The failure and advisory patterns further down the page are still drawn from real tests and are worth reading.

What do testers most often warn about on a Porsche 928?

The most common advisory is "Fluid leaking excessively and likely to harm the environment or to pose a safety risk to other road users", noted on 14.9% of all Porsche 928 tests. An advisory is not a failure: it flags something that will likely need attention before the next test.

What mileage does a Porsche 928 usually have at its MOT?

The average odometer reading recorded at test is 104,845 miles. This is the mileage across all tested examples of every age, not an annual figure, so treat it as a description of the fleet rather than a target for one car.

Model reliability file

Porsche 928 MOT pass rate & common failures

From 650 recorded MOT tests of the Porsche 928, published by DVSA.

Data updated 29 July 2026

Quick answer

Across 650 MOT tests, 81.1% of Porsche 928 tests ended in a pass. This figure is not adjusted for age or mileage, so it is not a reliability ranking: the Porsche 928 fleet does not yet cover a wide enough spread of ages and distances to compare it fairly against other models. Its most commonly recorded failure is obligatory rear fog lamp missing, or a front or rear fog lamp inoperative or in the case of a multiple light source more than 1/2 not functioning, which appears in 20.5% of failed tests. Cars of this model average 104,845 miles on the odometer when tested.

At a glance

Recorded pass rate

81.1%unadjusted, not comparable650 tests

We are not publishing a ranking for the 928. The examples tested do not cover a wide enough spread of ages and mileages to compare it fairly, and an unadjusted pass rate mostly sorts models by how recently they were bought rather than how well they were built. The failure and advisory patterns below come from the same 650 tests and are worth reading on their own terms.

DVSA recorded wording

Most common failure items

Share of failed Porsche 928 tests in which each item was recorded. One failed test often lists several items, so these do not sum to 100%.

1.An obligatory rear fog lamp missing, or a front or rear fog lamp inoperative or in the case of a multiple light source more than 1/2 not functioning20.5%
16 occurrencesLamp not working explained
2.The aim of a headlamp is not within limits laid down in the requirements20.5%
16 occurrencesHeadlamp aim incorrect explained
3.Windscreen washers not working or not providing sufficient fluid to clear the windscreen15.4%
12 occurrencesWiper or washer not working properly explained
4.Wiper blade missing or obviously not clearing the windscreen14.1%
11 occurrencesWiper or washer not working properly explained
5.A transmission shaft constant velocity joint boot missing or no longer prevents the ingress of dirt etc14.1%
11 occurrencesDriveshaft CV joint gaiter split or missing explained
6.A lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning12.8%
10 occurrencesLamp not working explained
7.Steering rack gaiter or ball joint dust cover missing or no longer prevents the ingress of dirt etc12.8%
10 occurrencesSteering rack gaiter split, damaged or missing explained
8.A headlamp or light source missing, inoperative or more than ½ not functioning in the case of LED11.5%
9 occurrencesHeadlamp not working explained
9.Significant brake effort recorded with no brake applied indicating a binding brake10.3%
8 occurrencesBrake binding or imbalanced across an axle explained
10.Windscreen washers not working or not providing sufficient fluid to clear the windscreen10.3%
8 occurrencesWiper or washer not working properly explained

Warnings without a failure

Most common advisories

Share of all Porsche 928 tests carrying each advisory. The denominator differs from the failure list above because an advisory can be issued on a car that passed.

1.Fluid leaking excessively and likely to harm the environment or to pose a safety risk to other road users14.9%
69 tests
2.A tyre seriously damaged8.7%
40 testsTyre damaged or deteriorated explained
3.A wheel bearing with excessive play6.9%
32 testsWheel bearing has excessive play or is rough explained
4.Play in steering rack inner joint(s)6.1%
28 tests
5.Brake disc or drum excessively weakened, insecure or fractured6.1%
28 testsBrake disc worn, pitted or scored explained
6.A spring or spring component fractured or seriously weakened5.6%
26 testsRoad spring broken or fractured explained
7.A suspension pin, bush or joint excessively worn5.6%
26 testsSuspension arm bush worn explained
8.Fluid leaking excessively and likely to harm the environment or to pose a safety risk to other road users5.2%
24 tests

What gets tested

The 928 fleet

Average mileage recorded at test: 104,845
Fuel mix of tested cars: Petrol100.0%

Trim names grouped into this model (4)

Recorded exactly as DVSA holds them. Trim-level names are rolled up so one model is not split across a dozen thin pages.

928 GT
928 GTS
928 S
928 S AUTO

Check a specific Porsche 928

A model average tells you the pattern. Its own MOT record tells you the car.

Compare within the range

Other Porsche models

Porsche 911 — 89.5% adjusted
Porsche Macan — 89.5% adjusted
Porsche Boxster — 85.7% adjusted
Porsche Cayenne — 85.3% adjusted
Porsche Cayman — 87.2% adjusted
Porsche Taycan — 91.0% unadjusted
All Porsche models

Common questions

How reliable is the Porsche 928 compared with other cars?: We do not publish a comparison for the Porsche 928, because the cars of this model that have been tested do not cover a wide enough range of ages and mileages. Its raw pass rate is 81.1% across 650 tests, but comparing a raw rate between models mostly ranks them by how new they are rather than how good they are. The failure and advisory patterns further down the page are still drawn from real tests and are worth reading.
What is the most common MOT failure on a Porsche 928?: The item recorded most often is "An obligatory rear fog lamp missing, or a front or rear fog lamp inoperative or in the case of a multiple light source more than 1/2 not functioning", which appears in 20.5% of failed Porsche 928 tests. Because one failed test can list several items, these shares do not add up to 100%.
What do testers most often warn about on a Porsche 928?: The most common advisory is "Fluid leaking excessively and likely to harm the environment or to pose a safety risk to other road users", noted on 14.9% of all Porsche 928 tests. An advisory is not a failure: it flags something that will likely need attention before the next test.
What mileage does a Porsche 928 usually have at its MOT?: The average odometer reading recorded at test is 104,845 miles. This is the mileage across all tested examples of every age, not an annual figure, so treat it as a description of the fleet rather than a target for one car.

How this was worked out

Method and limits

Figures come from the DVSA anonymised MOT testing dataset, published under the Open Government Licence. Only class 4 initial tests are counted: retests are excluded so a car appears once, and abandoned tests are excluded entirely. No adjusted rate is shown because this model's tested examples do not cover enough of the national age and mileage range for standardisation to mean anything.

An MOT measures whether a car met a legal standard on the day. It is not a breakdown record, a service history or a running-cost estimate, and a pass rate is a property of a fleet rather than a prediction about one car.