We own 3 R56s, all over 100K miles. One may have a dirty cat and we are wondering if it is possible to clean it with some additive - without taking it out and using lacquer cleaner per Scotty Kilmer, or gosh forbid needing to replace the thing.

I did some searches on the forum first but didn't find anything.

Also - that aside - if anyone has really good experiences with other additives for fuel injection - please share also!

Any Experiences to Share?

THANK YOU!

 

I am a firm believer that if the car is running correctly, then off-the-shelf additives are not needed. Often, fuel additives cause issues with cat converters. That being said, I have used those things and “thought” I felt a difference.

What make you think your cat needs cleaning? Did it fail a smog test?

 

I've often wondered about the cat cleaners. I've read hundreds of reviews that would tend to indicate that there are a lot of people having success using them.

A couple provisos though - if a cat is well and truly "worn out" (the magic metal that makes it work missing or damaged) then nothing short of replacement will do the job. But cats DO get dirty, usually from the engine having a misfire (raw fuel making it into the cat) or oil consumption. Often all it takes to "fix" this problem is a road trip, and maybe some spirited driving (where mashing the skinny pedal to the floor can cause the internal catalytic converter temperature to skyrocket, effectively burning off a layer or two of gunk). It kind of makes sense that a cat cleaner could help with this process, and possibly save a speeding ticket in the process... "but officer sir, I was just trying to clean my catalytic converter by going 120mph...".

 

Good to know I'm helping the cat last longer every time I track my car!

 

As Habby said - when the metal's gone, so is the magic of 'conversion'.

I can't say I've ever had a car fail because of a spent converter, but I'm sure it's bound to happen at some point. I'm invested in the pair of Gen II cars I currently own and they're both over 14 years old, sitting around 125,000 miles each.

 

Regarding Catalytic Converter Cleaners and do they work. I just used Rislone 4720 Fuel & Exhaust Emission System Cleaner successfully. The Check Engine Light went out within 150 miles of driving at freeway speeds. I have a 2013 R56 Base Cooper that had a Check engine light illuminate @ 290,500 miles. This saves me the $3500.00 to replace the Catalytic Converter quoted by the Local BMW Garage.

 

$3500 = $1100 for a new
converter, $600 for actual
labor, and $1800 for the
time it takes for the service
manager to laugh all the
way to the bank.

 

At 291,000 miles, there is no catalyst remaining.

My guess would be that at highway speeds, the engine operates efficiently enough that emissions are within tolerance. Don't be surprised when the CEL illuminates again in the not so distant future.