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Gas engine converter vs diesel engine converter

Edmund Schwenk, Metallurgist/CEO of Noble6, formerly PGM Recovery Systems, a US-based automotive precious metals experts, discusses the difference between CATs for gasoline and diesel engines and their value to the auto recycler.


Gas Engine Converter vs Diesel Engine Converter p
Edmund Schwenk

In the catalytic converter recycling industry, we get a lot of questions about the various types of catalytic converters and the value associated with each type. All fossil-fueled vehicles require a catalytic converter to meet emission control standards. Depending on the vehicle type, each has a different quantity of precious metals. When you recycle catalytic converters, the value of the precious metal loadings found within the ceramic monolith is what you get paid for. Three valuable precious metals found inside are platinum, palladium, and rhodium. This article will explain the differences between the two most common types of catalytic converters; one for a gasoline engine and one for a diesel engine.

What is a catalytic converter’s purpose?

The catalytic converter is responsible for converting toxic emissions from the internal workings of your vehicle into safe, breathable air. It achieves this by catalyzing approximately 90% of toxic emissions through chemical reactions involving rare earth elements such as platinum, palladium, and rhodium. Because these essential, precious metals are so valuable, there is a high demand for recycling catalytic converters. Recycling these precious metals from components that already contain them is far more cost-effective than mining them from the earth. However, the value varies greatly depending on the type of converter recycled.

Gasoline Engine Converters


Catalytic converters for gasoline engines have a high value. This is because precious metal loadings are becoming increasingly dense as emission standards become more stringent. More precious metals are required within the converter to function properly and keep our air clean. Platinum, palladium, and rhodium are the precious metals used in these catalytic converters.


The catalytic converter is often found near the exhaust manifold of an engine. Because the converter is exposed to very hot exhaust gases, it heats up quickly, allowing it to reduce unwanted emissions during the engine warm-up period. The converter can heat up and activate the catalyzation compounds faster the closer it is to the engine.

Diesel engine converters

Each diesel-powered vehicle is equipped with a catalytic converter that will convert carbon monoxide into carbon dioxide and break down any unspent fuel. This is known as a diesel oxidation catalyst (DOC).


Catalytic converters for diesel engines are less valuable than those for gasoline engines. This is due to the low cost of the materials used to manufacture catalytic converters, as well as the fact that the precious metals contained within are far less dense. This is because diesel fuel is cleaner than gasoline. When the fuel is burned, it does not produce as much carbon dioxide when compared to gasoline. Furthermore, the precious metals found contain only platinum and palladium, not rhodium.


A diesel engine, unlike a gasoline engine, lacks spark plugs; instead, diesels use compression ignition and glow plugs to heat the combustion chamber to aid ignition when the engine is cold. As a result, the catalytic converter is installed downstream of the exhaust manifold.


Catalytic converters, in a nutshell, reduce toxic emissions produced by a vehicle’s internal workings. The density of precious metal loadings in gasoline engine converters versus diesel engine converters accounts for the difference in value. A diesel engine converter contains fewer precious metals because diesel fuel is cleaner and produces fewer toxic emissions. As a result, fewer emissions need to be catalyzed, resulting in fewer precious metals and lower recyclable values. The location of these two converters is also a distinguishing feature. In a gasoline-powered vehicle, the converter is usually located closer to the engine, whereas, in a compression-fired diesel engine, the diesel oxidation catalyst is usually located downstream of the exhaust manifold.

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