On a 300SDL, whats the difference between a trap oxidizer and an oxidation catalyst?
 

The vehicle is an '87 300SDL. The previous owner told me that the trap oxidizer was removed in favor of an oxidation catalyst. What is the difference between the two?

I have started using Redline Diesel Fuel Catalyst but started wondering if this would be harmful to the oxidation catalyst. I have read on previous posts that the DFC was harmful to the trap oxidizer but what about the new oxidation catalyst?

Herb
'87 300SDL
'82 240D

MB had an emission recall on the Trap Oxidizers about 4 years ago, after all of the cars were at least 10 years old. MB installed under chassis catalyst instead of the original that was under hood. They have the same basic function.
ANY fuel conditioner that has small traces of any "heavy" metal(ie;lead, or copper) will damage either STYLE.

The trapox was attached directly to the exhaust manifold, upstream of the turbocharger. It's a vaguely football sized-and-shaped (Uh, US football, that is...) thing right next to the valve cover. If it has been removed you'll instead have a straight pipe in that location, covered with some shiny aluminum insulation.

The trapox was literally a soot filter. It was composed of a ceramic matrix built on steel rods. It literally trapped carbon particles. In theory it got hot enough to eventually burn the trapped carbon, reducing it to CO2. In practice, it didn't always work. Cars which did not see at least occasional aggressive use had the trapox slowly plug. Initially performance was reduced, eventually the engine overheated. Some have blamed the occasional OM603 head failures on this overheating, but I don't think there's 100% correlatation.

Another failure mode of the trapox was for small particles of the ceramic matrix to break loose and sail down the exhaust stream. This was rather unfortunate, as the next thing downstream was the turbocharger. When the ceramic material impacted the turbine blades spinning at 100K RPM, well, let's just say it was ugly and MB gave away more than a few free turbos.

The oxidation catalyst performs much the same function, though I believe it is constructed more like a typical catalytic converter. It doesn't literally trap the soot particles, in other words. It's located downstream of the turbo, where it can't do quite so much harm.

- Jim

MB DOC.

So far, I have only used poured one bottle of Redline DFC and driven about 30 miles. Should I drain out the tank and refill with regular diesel, or would it be ok to burn this fuel already have in this tank? In other words, will one bottle of DFC hurt the oxidation catalyst that is on now?

Thanks

Herb
'87 300SDL
'82 240D

Once shouldn't hurt!! Long time usage would kill it though.