Which parts fail
Components named in complaints (engine, cooling system, oil leaks, timing chain, exhaust).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2015 Mercedes-Benz C300 owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 2015 Mercedes-Benz C300. The contact stated that while driving approximately 50-60 MPH, the #1 piston cracked. The contact stated that while his daughter was driving, the vehicle was shaking and smoking. The check engine warning light illuminated. The vehicle was towed to an independent mechanic and the contact was informed that the #1 piston was cracked, engine cooler, P0301 cylinder #1, P219 solenoid failure. The vehicle was taken to another independent mechanic and the engine was replaced. The contact called the local dealer, but the vehicle was not diagnosed or repaired. The manufacturer was notified of the failure, but no further assistance was provided. The failure mileage was approximately 105,102.
I was in middle line on I-5 SB San Diego doing 40-60MPH when my car suddenly started to shudder, shake and smoke came from the exhaust. The car lost power and the check-engine light came on right away. I was told that Cylinder 3 lost pressure, that the engine wall was damaged and that possibly the piston and wrist pin are cracked. My car has only 66K miles and the Mercedes Benz dealership is telling me that I need a new engine that will cost $19,000. After doing some research I have found out that I wasn't the only one with this issue. I have listed an example here: "HERE IS A MAJOR ISSUE WITH THE 2015 M274 MERCEDES ENGINE REGARDING THE WRIST PINS. MERCEDES HAS ISSUED NUMEROUS INTERNAL SERVICE BULLETINS ABOUT THE ISSUE. THE ENGINES WERE MANUFACTURED WITH WRIST PINS WITH TOO MUCH TOLERANCE THAT SLAP AGAINST THE PISTON WHEN OPERATING THAT COULD LEAD TO PREMATURE ENGINE FAILURES. …
My son's car was blowing white smoke out of the exhaust and had a sweet burning smell and the check engine light came on. The crankcase vent valve is needing to be replaced on this 2015 C300 Mercedes Benz and many owners of this same type of car (different year) are posting about it. Owners of these types of cars are saying that replacement is happening more than once! That it's a common defect of these cars. My son has less than 100,000 miles (61,000 if that) and this shouldn't be happening. And, it's time someone does something to protect the consumer. Mercedes-Benz dealers are taking advantage of consumers and charging ridiculous prices to replace this part, but the part shouldn't be breaking. …
The contact owns a 2015 Mercedes-Benz C300. The contact stated that approximately every 6-8 months, the vehicle sputtered while driving at various speeds or while idling. The contact stated that a month after the first failure had occurred, the front end of the vehicle lowered as if the shocks or hydraulic system had failed. The failure had occurred 3 times within a year and a half. The contact stated that after the second failure, the entire vehicle lowered several inches, and at the third failure, only the front end of the vehicle was lowered. The dealer diagnosed the vehicle and determined that the hydraulic pump and the connections from the shocks to the hydraulic pump had failed. The failure reoccurred approximately 8 months later. The vehicle was returned to the dealer who diagnosed the same failure and completed the same repairs. …
The contact owned a 2015 Mercedes-Benz C300. The contact stated that while idle, the engine would vibrate with an abnormal sputtering sound coming from the engine. As the failure persisted, the check engine warning light illuminated. The contact had initially taken the vehicle to a dealer and the spark plugs were replaced; however, the failure persisted. The vehicle was returned to the dealer and a diagnostic test was performed, and it was discovered that an engine cylinder had blown. The vehicle was diagnosed with engine failure and the contact was provided an estimate for the repair. The contact then spoke to an independent mechanic who informed her that the failure was a common failure for her model vehicle. The manufacturer was also notified of the failure and a case was filed. …
The contact owns a 2015 Mercedes-Benz C300. The contact stated while driving 40 MPH, the vehicle unexpectedly veered to the left. There was no warning light illuminated. The contact stated that the steering wheel became inoperable, and the contact was unable to straighten the steering wheel. The brake pedal was also depressed. The contact attempted to depress the accelerator pedal however, the vehicle started to stall. The contact pulled over into a parking lot and was able to restart the vehicle. The dealer was not contacted. The vehicle was not diagnosed or repaired. The manufacturer was not made aware of the failure. The approximate failure mileage was 82,000.
The contact owns a 2015 Mercedes-Benz C300. The contact stated while driving 25 MPH, the check engine warning light illuminated. The contact veered to the side of the road. The vehicle was towed to an independent mechanic, where the diagnostic test retrieved code: P052E, and it was determined that the positive crankcase ventilation (PCV) valve had failed and needed to be replaced. The vehicle was not repaired. The dealer and the manufacturer were not notified of the failure. The failure mileage was approximately 125,000.
The contact owns a 2015 Mercedes-Benz C300. The contact stated that while driving at an undisclosed speed, the vehicle hesitated and stalled. The check engine warning light was illuminated. The vehicle was towed to Safety Auto Repair where it was diagnosed that the engine failed and needed to be replaced. The vehicle was not repaired. Neither the dealer nor the manufacturer was notified of the failure. The failure mileage was approximately 90,449.
In March of 2020 I was driving home from work. I stopped at a red light. When it turned green, I proceeded to step on the gas. My car started making noises and shaking as I drove. My check engine light came on. I was able to pull over without incident. My vehicle has under 48k miles on it! I had it towed to a Firestone facility by my house. They replaced spark plugs and ignition coil 1 and 2. They said it was still severely misfiring. Cylinder 1 must have internal damage and should be towed to the dealer. They gave me a spark plug they removed that had significant damage to the top part. They said something must have impacted it with significant force. I then had the vehicle towed to a Mercedes Benz Dealership. They said they inspected with a scope and found piston material missing, can see ring exposed and have damage to cylinder wall. …
The wrist pin is defective in early engines during manufacturing. It is not safe to operate the vehicle because at any time without any warning this can cause fatal damage to the engine - piston crack resulting in total loss of control even at high speeds on the highway. Numerous complaints were filed on NHTSA regarding cracked pistons most likely related to this wrist pin manufacture defect. The problem is acknowledged by M-BENZ (NHTSA ID Number: 10058545), and starting around April 20 2015 M-BENZ started to install modified wrist pins to prevent future failures, but they did not address existing faulty wrist pins. …
NHTSA investigations
C300 Wrist-pin allegation
In a letter dated April 29, 2022, Mr. Sergio Betancourt (the petitioner) submitted a petition attributing engine failure of his 2015 Mercedes-Benz C300 to "wrong sized wrist-pins" and asserted that these were prevalent on all Mercedes-Benz models (including the Metris minivan, GLC300, and C300) equipped with a version of the M274 engine.
Engine complaints in other C300 years
Frequently asked questions
How common are engine problems on the 2015 Mercedes-Benz C300?
NHTSA has 128 complaints about the engine & cooling of the 2015 Mercedes-Benz C300, 34% of the model year's 381 complaints. The component named most often is cooling system (1 mentions).
Is there a recall for 2015 Mercedes-Benz C300 engine problems?
No. NHTSA lists no engine & cooling recall for the 2015 Mercedes-Benz C300, though it has 11 recalls for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2015 Mercedes-Benz C300 engine problems start?
Half of the complaints with a recorded mileage happened before about 53,000 miles, and 28% before 25,000 miles.
Is it dangerous?
Owners linked 0 crashes, 1 fire and 0 injuries to engine & cooling problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.