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Originally Posted by ke4jr
Could some one please elaborate and explain what it means and whats it for... Thanks
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DEF is "diesel exhaust fluid". It is specifically designed to inject into a reaction chamber in the exhaust system for the purpose of reducing the level of NOX in the exhaust to levels required by the EPA. All engines built after 1/1/2010 must comply with those levels. By stockpiling engines built before 2010, the chassis builders effectively put off this requirement for motorhomes until the 2011 model year. DEF is sold at big box stores and truck stops primarily. In terms of EPA requirements, Diesel engines had 3 major dates when big requirements were imposed:
1. 1/1/2004 was when the first round of NOX reduction took place. The primary device used was EGR (exhaust gas recirculation).
2. 1/1/2007 was when the mandate for ULSD (ultra low sulphur diesel) took effect and the requirement for a DPF (diesel particulate filter) was required. These two events were tied together because ULSD kept the sulphur in the fuel from destroying the DPF. Again this took place in motorhomes with the '08 model year.
3. 1/1/2010 was the mandate for a major reduction in NOX. The primary tool was the usage of DEF to react with the exhaust stream.
These three steps along with many smaller incremental steps have driven the cost of a Diesel engine by nearly 100%.
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