A small symbol such as a star, or letters like MO, AO or N, marks a tyre as OE-approved, developed and signed off for a specific car maker. These are also called homologation or original-equipment markings, and they tell a useful story about how the tyre was built.
What an approval marking means
Car makers often want tyres tuned precisely to a particular model, its weight, suspension geometry, performance targets and even the noise frequencies its body amplifies. So they work jointly with a tyre manufacturer to develop and validate a tyre for that car, and once it passes, it carries the maker's approval mark on the sidewall.
An approved tyre is therefore more than a standard tyre in the same size: it has been tuned to that brand's requirements. A standard tyre meets the legal type-approval rules; an OE-marked tyre goes further to match the car maker's own targets.
The common approval marks
The marks most often seen on UK roads are:
| Mark | Car maker |
|---|---|
| ★ (star) | BMW and Mini |
| MO | Mercedes-Benz |
| AO | Audi |
| N | Porsche |
| K | Ferrari (Michelin) |
| T | Tesla (Michelin) |
Several of these have variants. Mercedes uses MOE for an approved run-flat and MO1 for AMG models; Audi uses RO1 for Audi Sport. Different tyre brands carry the same car maker's mark, since more than one supplier can earn approval.
Reading the Porsche N marking
Porsche's system carries a little more detail. The N stands for Nürburgring, where the tyres are tested. N0 is the first approved version of a design, and N1, N2, N3 and so on mark later evolutions as the compound or construction is refined.
On cars from around 2019, Porsche added a second letter to identify the model line, to stop the wrong approved tyre being fitted. So NA is the 911, NB the 718, NC the Cayenne, ND the Panamera, NE the Macan and NF the Taycan, meaning a marking like NA0 reads as the first approved 911 tyre.
A newer marking: HL
On some tyres, particularly for heavy electric vehicles, an HL (High Load) marking appears before the size. Introduced in 2021, it indicates a load capability above even an Extra Load tyre of the same size, reflecting the extra weight of EV battery packs. It relates to load rather than approval, but it increasingly appears alongside OE markings on cars that need it.
Do approved tyres have to be fitted?
There is no legal requirement to fit OE-approved tyres. The car maker recommends keeping to the original approval so the car behaves as it was developed to, particularly on performance and premium models, but a good non-approved tyre in the correct size, load index and speed rating can be fitted instead.
The sensible rule when going either way is consistency: fit a full matching set of the same tyre rather than mixing an approved tyre with a different non-approved one, so grip and behaviour stay balanced across the car. The OE-approved version to match what the car came with is easy to find by size at a specialist tyre site such as Tyres.co.uk.
From the workshop: the marks matter most on premium cars where the maker tuned the tyre to the chassis. We will always offer the matching OE tyre, but if a customer prefers a quality non-marked tyre, the key is fitting them as a proper set, not one odd one out.
Sources and accuracy. The approval marks and the Porsche model coding here reflect current car-maker practice at the time of writing, and makers do add or revise markings over time. For a specific car, the handbook and door placard are the reference. If anything here looks wrong, get in touch and we will check it and put it right.
Common questions
What does a star on a tyre mean?+
A star symbol means the tyre was approved by BMW (and Mini), developed and tested with the car maker for their vehicles. Other makers use their own marks: MO for Mercedes-Benz, AO for Audi and N for Porsche.
What do MO, AO and N mean on a tyre?+
They are manufacturer approval marks. MO is Mercedes-Benz, AO is Audi and N is Porsche. Each shows the tyre was co-developed and validated for that brand's vehicles, tuned to their weight, suspension and performance.
Do I have to fit OE-approved tyres?+
No, there is no legal requirement. The car maker recommends matching the original approval for the intended handling and refinement, but a quality non-approved tyre of the correct size and rating can be fitted. If doing so, it is best to fit a full matching set.
What does the N number after the Porsche mark mean?+
On Porsche tyres, N0 is the first approved version of a design and N1, N2 and so on are later evolutions. On cars from around 2019, a second letter identifies the model, for example NA for the 911, NC for the Cayenne and NF for the Taycan.