This briefing is a comprehensive technical overview of the Euro 6 engines emissions standards, which tighten limits on air pollutant emissions set in previous European standards and require the best technology currently available for vehicle emissions control.

Countries outside of Europe, the United States and Japan have largely patterned their emissions policies on European regulations and the associated mandates for clean, low-sulfur fuels. By adopting the Euro 6/VI vehicle emission standards, these countries can achieve up to a 99 percent reduction in the emission of pollutants like fine particulate matter (PM2.5), reducing the risk of ischemic heart disease, lung cancer, stroke, and asthma.

European emission standards regulate gasoline and diesel vehicles separately. Considering first the standards for diesel vehicles (see Table 1), Euro 6 is a significant advancement over Euro 5 with regard to NOX limits. The NOX limit declines from 0.18 g/km to 0.08 g/km, a reduction of 56%. Explicit NOX limits were introduced at the Euro 3 level, and in the Euro 6 standards the NOX limit is 84% lower than the Euro 3 level. This has significant implications for control technologies, requiring for the first time the integration of emission control aftertreatment for NOX emissions, such as selective catalytic reduction, lean NOX traps, or others.

The particle mass and particle number standards for diesel cars in Euro 6 are the same as those in Euro 5. Limits on particle mass emissions for diesel cars have nonetheless been reduced by large amounts since the Euro 1 standards were introduced. The Euro 6 particle mass limits for diesel cars represent a reduction of 96% from Euro 1 limits. The particle mass limits are now so low that measurement accuracy and sensitivity are an issue, which has prompted the introduction of limits on particle number, which is easier to measure. These limits were first introduced at the Euro 5 level. Particle number limits are also supported by research in Europe that has found significant health impacts from exposure to high particle number counts.

The limits for gasoline vehicles have also fallen significantly, relative to earlier European emission standards. The Euro 6 NOX standards for gasoline cars are the same as those for Euro 5, but they are 60% lower than those for Euro 1. Mindful of attempts by car manufacturers to improve the fuel consumption of gasoline vehicles through gasoline direct injection (GDI) technology, European regulators introduced particle mass limits on GDI engines at the Euro 5 level, equal to the limits set for diesel vehicles. Limits on particle number emissions of GDI engines were introduced in Euro 6 (they were introduced at Euro 5 for conventional diesel cars), and they are numerically the same as those for diesel cars. Europe phased in the Euro 6 particle number limit on GDI engines over the first three effective years of the standards. This more lax standard is 6.0 x 1012 #/km, an order of magnitude less stringent than the diesel standard (and the ultimate Euro 6 GDI limit) of 6.0 x 1011 #/km. This three-year phase-in was intended to extend the period of research and development needed to meet the standard, and by 2017 automakers are expected to meet the more stringent