Same experience when testing a c250d and when moonroof is open. When closed no smell.

Seems like somehow this is the culprit.

The cause of the smell is 'cosmoline'. some sort of grease on engine or parts from Germany to protect from oversea delivery. The odor is way too strong. I don't know how people stand on those kinda smell when buy a new MB cars.

I spoke w dealer shop they want me run over 5k miles. so basically I can't open windows or moon-roof for 5k. It's ridiculous reason I can't get fresh air from outside.
My car is around 4k. I still smell..but it's weak but still there. The smell was like rotten rat inside of my car first time ..then..it's like rotten rat's tail with my car.

MB Tex off gassing???

No such smell with my car. My BMW however has a typical hot exhaust/sealant smell after hard driving. Not off putting, I just smell it when exiting the car after a blast.

Porsche also is famous for new car odors that are commonly blamed on the use of cosmoline. I checked on this, since it really doesn't make much sense to use such an old and messy preservative on a brand new car. I have yet been able to find a single car maker that currently uses cosmoline on any components of their new production vehicles. Years ago, it was not uncommon to apply it to some metal parts, but now more modern preservatives are used. Also, the smell of burnt cosmoline is nothing like what is being described here.

Blaming the use of cosmoline for assorted new car odors is an easy way for dealers to avoid the real problem ... whatever that may be.

I've noticed it recently too...much like oil on a warm surface. Done 3000 miles in the 5 weeks since I got the car, hopefully it'll settle down. I don't notice it all the time, moreso on warmer days

I wrote a couple weeks back about a rancid smell coming thru the car with the windows & sunroof open. It has a metallic smell but also mixed with some type of water getting foul.

When I was young my parents had a metal sink by the washer. If water pooled and remained you would get that oder.

It does not occur with the Airconditioning on . I made an appointment with the dealer . They said there was a treatment. left it there ( did get a loaner ).

When I got back they said that they could not find the oder but they did not try it with the air off.

I was kind of frustrated . I know Stan in the White Mountains will laugh but its over 20 miles each way to the dealer LOL.

I was able to smell it again with the air off and window and roof open. It's not as bad but it not the new car smell or leather we would hope for.

Wonder if that is what we are smelling. I noticed people have taken photos or recorded sounds that should not be there. Anyone know how to send smells thru the form .

No, I won't laugh at all. I'm well over 100 miles away from my dealer, but the trip is almost entirely on highways with posted speed limits of 70 mph. The trip takes about two hours each way, but it's still better than a shorter trip through heavy city traffic. Regardless of the distance, a trip to the dealer's service department is never how one wants to spend their time.

I hope the problem with the odor in your car is eventually diagnosed and successfully eliminated.

Most dealers will take it for granted that it is a bacterial infestation of the HVAC evapourator & pipework. If not they tend to be stumped.

I get a smell when I open the pano roof, smells like lubricant or something, I assumed it was something that is applied to the mechanism of the roof. My cars done 7500 miles and its been present since I took delivery and it's still there now at the same potency.

I too experience this smell when opening the pano roof.

I just noticed, with the roof open, that there is a very heavy coating of lubricating grease on all the rubber seals. I wonder if this could be the source of some of the smells being reported here.

I experience this smell too when I open the pano roof and windows. I've had my car for approximately 5 months and I'm almost hitting 10K miles and the smell is just as strong as it was when I purchased the car.

Had the pano roof wide open all day, today.

No smells, whatsoever. (As per Stan's comment, mine too has a heavy dose of lube on the seals).

It's nearly a year since I got c300(8k miles..) with cosmoline smell. Some people are very sensitive about it like me. It makes headache. the odor still there whenever open moonroof or windows open while driving.


It has been a year. It's nice weather in AZ now but I can't drive while opening windows and moon roof. it's absolute ridiculous. Do I have to get over the headache? or just get rid of the car?

Update: March 24 2016


I have drove this car around a year and around over 10k miles.
Still the odor is there. It's like someone spray a paint in the car when open Moonroof or Windows. Very weaker than before but still there.
I want to breath fresh air.


__________________________________________________ _______
Here is dealership experiences:


Three times of services and the smells still there.
Basically they can't find the issue of the odor and just washed car again and again.
I had services one time at Scottsdale MB dealership, and two times of Schumacher in N Scottsdale in AZ. I bought my car at the Scottsdale MB but the repair person didn't want to hear any this kinda issue and hung up and didn't answer the phone.(No call back either, awful dealership services)


I changed to Schumacher dealership in North Scottsdale Arizona. Schumacher is much nicer and tried to figure it out but nothing changed.


I realized that last two C classes I loaned cars doesn't have any smell. They are like under 1k miles. Same spec with panorama moonroof. So it's earlier version of C class or something not right on my car.

If it's so obvious then you should be able to easily demonstrate it to any service advisor on a test drive. Getting acknowledgment of the issue is the first step to resolution. Just because they can't find the source doesn't make it go away. Next step is to call MB North America and file a complaint there.

Very interesting to know that others also report strange smells. My car is one year old, and I can smell something like the burning wire at the front of the car. There is no smell while I am driving, only when I park in my garage, and I am standing in front of the car.

My dealer checked it and they could not find the source, but it is still there.

Likely root cause: Non-solvent grease excessively applied to the rails and seals of the pano roof.
Solution: Put on some gloves, grab a lint free microfiber cloth, and wipe it off.

A friend of mine used the same kind of grease for an AR15 build that we put together in my workshop. The smell is pretty awful but it usually dissipates over time. If it's persisting this long, the amount of grease was excessive. Wipe off the excess and the smell will dissipate.

I have this smell when underway with the sunroof open, very annoying. with AC both on and off, from speeds of about 40mph +

Nothing that a little tree car freshener hanging on the rear view mirror could fix

I recently bought a cpo 2015 c300 and experience the same issue with either opening the windows or the sunroof. Wondering if anyone found a resolution to this strange issue?

Nope, I sold the car. You have to deal with it. Some mb cars has the odor which I drove loaner cars. I couldn't find the cause of the odor either nor technicians. They can recognize the odor but no successful result.
It was not a good experience with C-class. Some C class I loaned from dealer didn't have the odor.