LMM Duramax and Oil Bypass Filters - Soot

Volume 2 Issue 1 - Diesel Articles

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LMM Duramax and Oil Bypass Filters
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Soot is a byproduct of the combustion process that begins as particles that are sub-micron in size. At that size, they pose no threat to the engine and if they remained that size, there would be no need (and it would be very difficult) to filter them. Unfortunately, soot particles are attracted to one another and join together to form particles that are big enough to cause damage but small enough to evade capture by the full flow filter. Soot is more readily produced in diesel engines than gasoline engines.

Today’s turbo-charged, computer controlled, fuel injected engines are extremely good at mixing air and fuel for clean burning engines. The Duramax engines prior to the LMM were as good, if not better, than most at burning cleanly; unfortunately, the requirements to lower emissions resulted in exhaust gas recirculation (EGR). Recirculation of exhaust brings up to 35% of soot back into the engine for re-burning. The soot levels for these engines are significantly higher than the preceding engines and the soot inevitably finds its way into the oil through the piston rings. High soot levels increase the viscosity of the oil and interfere with proper oil flow. When soot levels are high, soot begins to drop out of solution and can clog critical oil galleries and starve components of vital lubrication. The requirement to recirculate exhaust gases is one of the bases of the CJ-4 classification for diesel oils. CJ-4 rated diesel oils are designed to carry higher levels of soot and to resist soot dropping out of solution.

Oil Bypass Filters Flow Abrasives

Soot and other particles as small as five microns are responsible for the majority of abrasive wear in an engine. A good bypass oil filtration system will effectively remove particles to the three micron, and sometimes smaller, range.

Using CJ-4 oil in combination with the highest quality full flow filters will help keep soot in check to a point. However, the only way to ultimately remove the soot that remains unfiltered in a system is to drain the oil. This reality shortens the lifespan of oil and requires a higher frequency of oil changes than might otherwise be necessary, especially for extended drain synthetics. In the future, I believe that improvements in diesel oils and better full flow filters will allow for extended drain periods using the standard oil filter system. Using the technology available today, I recommend using a high quality synthetic CJ-4 diesel oil complemented by an oil bypass filters system that is capable of filtering out a portion of the soot. Excellent bypass systems remove 30 to 40 percent of the soot. Even at this level of efficiency, soot levels are manageable. Full flow filters by themselves essentially remove no soot from the system.


Variations of Oil Bypass Filters

Most bypass filtration systems leave the standard full flow filter in place and add a remotely-located bypass filter. These systems are the ones sometimes referred to as parasitic because they divert some of the oil away from the main oil flow responsible for the lubrication of the engine’s components. The amount of oil diverted is controlled by an orifice or similar restrictor to make sure that enough oil is reaching the engine. An alternate design, patented by Amsoil, locates both the full flow and bypass filter remotely.

Oil Bypass Filters Dual Remote System

The Amsoil dual remote filtration system eliminates the parasitic loss of oil flow to the engine.

This dual remote oil filtration system eliminates the parasitic characteristic of a typical bypass unit by routing all the oil, whether it travels through the full flow filter or through the oil bypass filter, to the engine components after filtration has occurred. As with the single remote bypass filter system, only a fraction of the oil travels through the bypass filter on a given pass.

Regardless of the design or manufacturer, the bypass system is a good investment on any diesel engine. For the LMM Duramax diesel engines, with EGR, the bypass is a necessity. Soot is a concern in all diesel engines but with the EGR system, soot levels can become destructive. A potential benefit of installing a bypass filtration system is extended oil change intervals. When using properly formulated synthetic diesel oil and a high quality bypass filtration system, it is possible to avoid the impact of higher soot levels and extend oil drain intervals significantly. If you own an LMM Duramax, you are simply protecting your investment by installing a good bypass oil filtration system.

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