What to check on a German BMW, Mercedes or Porsche

The Premium Cars team19 September 20266 min read

One important warning before we start. Neither the ADAC breakdown statistics nor the TÜV-Report publish data by engine code (B58, OM654, PDK, 9G-Tronic…): they publish by model and by age. Everything along the lines of "engine X has a reputation for…" comes from forums, not from a technical source. You will not read it here. And official campaigns do not talk about a "weak engine": they talk about specific parts, with a file number.

What applies to all three brands

The ADAC Pannenstatistik 2026 covers 158 model ranges from 27 brands, cars between 2 and 9 years old. Its most frequent causes of breakdown: starter battery 45.4 %, engine and engine management 21.8 %, electrical system 10.4 %, tyres 8.9 %, locks and keys 6.8 %. And one figure that matters if you are unsure about premium brands: in the list of the 16 worst models there is no BMW, Mercedes-Benz, Porsche or MINI.

The TÜV-Report 2026 (20 November 2025) covers 9.5 million inspections and 216 vehicle types.

BMW

What the reports say

The ADAC places among the models with fewest breakdowns the 1 Series, 2 Series and its Tourers, iX1, X2, 3 Series, 4 Series, i4, X3, 5 Series and X5.

But there is a counterpoint worth knowing: the TÜV-Report 2026 makes the BMW 5/6 Series the worst in its age group twice (at 4-5 years and at 8-9 years). The reasons the TÜV gives are specific and very useful:

The actuators of the active pedestrian-protection bonnet "have to be replaced every five years, which often does not happen". The TÜV notes that other BMW models carry the same bonnet.
Above-average defects on propshafts, on the emissions test and, in part, on springs and dampers.

The practical consequence, and this is our recommendation: on a BMW five years old or more, ask for evidence that the active bonnet components were replaced. The car's service indicator does not track it, so it is easy for nobody to have remembered.

Official campaigns to check

These are verified in the public NHTSA database in the United States (the German KBA register returned a 403 to us and we could not read it, so the models listed are the American ones):

File	What was wrong	Units
24V576000 → 25V644000	The starter motor can overheat. The remedy went from a software update to replacing the starter motor	105,588 → 145,102
26V056000	Wear on an internal starter motor component: it can overheat and catch fire. 2 Series, 3, 4, 5, X3, X4, Z4 from 2021-2024	87,394
24V739000 → 26V422000	Failure of the integrated braking module: loss of brake assistance or of ABS/DSC	11,579 → 428
23V821000	Defective weld on the transmission control unit cover: oil gets in and can lock it up	552
22V614000	Diesel EGR cooler: can leak coolant and cause a fire	298

This is the most important thing in the whole table: a campaign already carried out may need a second intervention. Cars fixed under 24V576 need 25V644; cars fixed under 24V104 need 24V739 and then 26V422. You have to check that the latest version has been done, not just "one". BMW lets you check it with the 17-digit chassis number.

BMW servicing does not run on fixed mileages

BMW uses Condition Based Service: sensors, time, mileage and driving profile decide when each service is due. The system tracks engine oil, vehicle check, front and rear brake pads and brake fluid (that one by date). Spark plugs, according to BMW's official booklet in the United States, every third or sixth oil service; cabin filter at the second. In Europe BMW does not publish the intervals on its website: they are in the car's service book.

Mercedes-Benz

What the reports say

Mercedes comes out very well here. The ADAC puts the A-Class, B-Class, EQA and GLB among the best, and no Mercedes appears among the worst. And the TÜV-Report 2026 gives Mercedes its long-term quality award for 10-11 year old cars, with an average serious defect rate of 18.5 %. The C-Class wins its category at 2-3 years and the B-Class the people-carrier one.

Campaigns to check

A note on method, and we mean it: we have no Mercedes campaign verified in an official source. The American database responds but returns no results for Mercedes passenger cars, and the German register did not give us these two. What follows comes from German specialist press, where several outlets agree on figures and codes, and we have not been able to reproduce the exact figures: we give them rounded and as a lead, not as fact:

Coolant pump and EGR valve on OM654/OM656 diesels (Mercedes code 2090008): built between January 2017 and October 2021; C-Class, E, S, GLC, CLS, GLE/GLS and G-Class. A possible leak between the coolant and vacuum circuits, with a fire risk. Around 800,000 cars worldwide and close to 240,000 in Germany.
Propshaft joint (code 4190026, May 2026): built between October 2017 and December 2019; E-Class, S-Class, GLC and CLS. Wear that can leave the car immobilised. Around 200,000 cars worldwide and some 37,000 in Germany. Note: it affects petrol cars as well as diesels, so it is not "a diesel thing".

Mercedes has its own page for checking whether a car is affected, and you can also ask at the dealer or in its app.

Porsche

Here we have to say what is not there

The ADAC Pannenstatistik 2026 contains no Porsche at all: they do not reach the minimum registration threshold the statistics require. And the TÜV-Report 2026 press release does not mention them either. So anyone telling you "the ADAC says this Porsche is reliable" is making it up.

Official campaigns

What we did find in the NHTSA data, consulting 911, Cayenne, Panamera, Macan and Taycan between 2016 and 2021: no campaign for an internal engine failure or for the PDK gearbox. There are campaigns on parts, and one on the gearbox oil circuit: on the 2020 Cayenne, an insufficient weld on a transmission oil pipe could cause a leak (20V271000). These are the main ones:

911 from 2021 to 2024 (and 2025 Panamera, 718 Cayman GT4 RS and 718 Spyder RS): the centre-lock wheel bolt can fracture and the wheel come off (24V809000). The most important on the list.
Cayenne (2021): the connection between the steering column and the steering box can fail (21V493000); and a rear trailing-arm nut that can break through stress corrosion (21V271000), with a follow-up alignment campaign afterwards.
Panamera (2017-2021): moisture in the external coolant pump of the climate control, with a risk of short circuit and fire (23V033000).
Macan (2016-2020): rear seat belt anchors not correctly tightened (23V443000).

Porsche does not publish its service intervals either: it says the maintenance plans are "precisely matched to your model". So we cannot give you a figure for when the oil or the PDK is due, because none is published. You ask the Porsche Centre.

What has to be in the service history, in short

Brand	What we look at
BMW	Services done when the CBS indicator asked for them; campaigns closed in their latest version (starter, integrated brake, EGR if diesel); and on cars five years or older, the active bonnet
Mercedes	Services according to the ASSYST indicator; and on 2017-2021 diesels, the coolant pump campaign; on E/S/GLC/CLS from 2017-2019, the propshaft one
Porsche	Servicing from the model's official plan recorded at a Porsche Centre; campaigns closed; and if it is an Approved car, an active warranty

You can see what is available right now and, if you already have a car in mind, work out the tax with the registration tax calculator.

Frequently asked questions

Is it true that the B58 or the OM654 give trouble?

Neither the ADAC nor the TÜV publish reliability by engine code, only by model and age. What exists are official campaigns on specific parts. Any claim about a particular engine comes from forums, not from a technical source.

How do I know whether a car has open recalls?

With the 17-digit chassis number, on the brand website or at the dealer. Importantly: check that the latest version of the campaign has been done, because several have been extended with a new remedy.

What does the TÜV say about the BMW 5 Series?

That it is the worst in its age group at 4-5 years and at 8-9 years. The reasons: the actuators of the active pedestrian-protection bonnet, which have to be replaced every five years and often are not, and defects on propshafts and at the emissions test.

And about Mercedes?

It gives Mercedes the long-term quality award for 10-11 year old cars, with an average serious defect rate of 18.5 %. The C-Class wins its category at 2-3 years.

What does the ADAC say about Porsche?

Nothing: no Porsche appears in its breakdown statistics because they do not reach the minimum registration threshold. Anyone quoting the ADAC about a Porsche is making it up.

How often does it need servicing?

BMW gives no fixed figure: the Condition Based Service system works it out. Porsche and Mercedes do not publish their intervals on their public sites; they are in the car service book.