Is there an aftermarket catalytic converter that will work for the OM617. I have an '85 300CD and while I don't mind the smell that much, it's a lot different than it was 40 years ago. Let's just say that people don't appreciate me idling in the elementary school pickup line.

If you still have tho original, call the dealer, you might still be able to get a deal on replacement. Otherwise, use a bypass pipe. I think Rollguy on this forum has them. If you have renewable diesel available in your area, switch to that. I get looks in the smug zones too.
BTW Electric cars pollute too, just not where they drive.

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Chris
84 280sl
82 300d euro

A diesel powered Mercedes uses a trap oxidizer. Catalytic converters are used on gasoline powered vehicles. The Mercedes trap oxidizer was a problem and eventually Mercedes provided a life time warranty on the trap oxidizer. Check with MBUSA or your dealer. The best solution, as already stated, is to use a bypass pipe that ROLLGUY sells. The bypass pipe or a new trap oxidizer will not eliminate the smell. You are driving a diesel which has its own smell.

I purchased a new 1985 300D in 1985 at the Mercedes dealer in Palm Springs. Within 100 miles of driving the engine would not run because the trap oxidizer was plugged. It took the dealer almost 2 weeks to receive a new trap oxidizer from Germany. Thankfully once replaced no additional problems.

I’m actually looking for trap ox alternative. I’m well acquainted with the trap ox. It’s gone for a multitude of reasons but it did work to significantly reduce the smell.

Magnaflow makes a series of passive SCR converters for diesels. Available at Summit, Jags etc.
With this option you will need to add it as close to the manifold as possible. Recommend post-turbo in the down pipe after the flex joint at the turbo exit. It needs to get hot enough to work and will reduce the odor quite a bit.

Where are you located? Here in Southern California, Chevron sells a Bio Diesel that my W123s run nicely on. Silver lining is that the exhuast is less smelly. Give it a shot.