Mercedes Benz Repair

How fragile is the DPF and Catalytic Converter?
DPFs and Catalytic Converters have been around for decades.  When it comes to the final cleanup of what goes out the tail pipe the DPF and Catalytic Converters do the heavy lifting.

For years the EPA has passed all sorts of regulations to make their lives easier.  One heavily regulated area is the motor oil that goes into your engine.  Most people could care less about motor oil.   It all looks the same to them.  It’s slippery and that’s about as far as most people get.

However, the EPA thinks a lot about motor oil.  They have long believed that as certain chemicals in motor oil are burned and vaporized, they damage the DPF and Catalytic Converters.  However, some of those chemicals are critical to the health of your engine.  Oil can’t do its job without them.

For this article I’ll stick to discussing zinc and sulfur.  Zinc is a very important part of oil.  It is the last line of defense before metal-to-metal galling occurs.  Engine oil needs about 1,400ppm to 2,000ppm for the best protection.  The EPA allows about 900ppm.

The most common myth about zinc is that it’s only needed in old engines with flat tappet lifters.  I won’t bore you with explaining what flat tappet lifters are, but the myth is wrong.  Zinc is needed in many areas of modern engines.

When the EPA lowered the zinc levels in the oil they said it was because zinc “poisoned” the DPF and the Catalytic Converter.  As soon as zinc levels were lowered Mercedes-Benz engines started having timing chain failures.  MB Service Bulletins LI05.10-P049909 and LI05.10-N-057796 are about OM642 and OM651 diesel timing chain failures caused by EPA recommended motor oil.

The timing chains were stretching and throwing off the Camshaft timing which finally causes engine failure.  The DPF and Catalytic Converter were in great shape, but the engine was ruined.  This is not a new problem.  It’s been happening for 25 years.  If it was so easy to replace zinc with something else, why haven’t they figured this out?

One of my former mechanics has been working at the Mercedes-Benz factory in Germany where they build V8 Diesel engines that go to China and Russia.  Those engines produce about 600hp and they have DPF’s and Catalytic Converters just like the engines that come to America.  So why does Mercedes only send those engines to China and Russia?   The answer is because Russia and China haven’t lowered the zinc levels in their motor oil.

So why doesn’t the extra zinc in Russian and Chinese oils poison the DPF and Catalytic Converters on those engines?   If you have better quality oil with all of the additives the engine won’t burn oil.  You only need to worry about zinc and the other stuff poisoning the DPF and Catalytic Converters is when the engine is burning oil.

The MB engines being sent to China and Russia are proof that the EPA does not understand how oil and engines actually work.  The DPF and Catalytic Converters will work just fine if the oil is high quality and isn’t burning.

So how do we get oil like they have in China and Russia?   We already have it.  It’s just called something different.  Since Dirt Bikes and some motorcycles don’t have emission equipment the EPA doesn’t regulate motorcycle oil.  There are also synthetic oils made for older engines that don’t have emission systems.  If you look at the Material Data Sheets you can find the oils actual chemical blend.

That gets us to the soot load in diesel oil.  Sulfur makes most of the soot.  Sulfur is in the fuel and oil where it serves many important lubrication functions, but it’s critical to have a sufficient amount.  The EPA has also reduced the sulfur content of fuel and oil (I’m leaving out a lot of details because this part would get to lengthy.  There is more to oil than just this, but these are the high points.)

Older diesel oils could handle much higher levels of soot.  Any oil with an older diesel rating will handle the new soot levels.  Or you could add BG “DOC” (Diesel Oil Conditioner) and it would give oil the additives to help with soot.  Change the oil filter every 2,500 miles and that will remove a lot of the soot.   The oil filters on the diesels going to Russia and China are much bigger than the oil filters coming to America.

The bottom line is this; protect your engine with the best oil – read my BlueTec Diesel Oil Blog for specifics.  The DPF and Catalytic Converter are tougher than you think.  It cost about $200 to clean the DPF and Catalytic Converters, a new engine however, cost $30,000.