As previously noted, exhaust emission regulations continue to drive the demand for new engine development.  The European emission regulations have resulted in a new generation of European heavy-duty diesel engines and diesel engine oils, driven by the requirement for stringent reductions in nitrogen oxides (NOx) and particulates.  European engine manufacturers aim to reach legislated emission levels with engine internal measures, such as combustion and general engine optimization as well as external measures, such as particulate traps. 

One consequence of this new technology is increased levels of soot in the oil, leading to durability concerns regarding soot-related wear.  Since low-emission technology increases the capital cost of new engines, customers are demanding lower operating costs. Consequently, there is a widespread demand for extended oil drain intervals, in addition to further improvements in durability and fuel economy.

ACEA periodically updates their category requirements and changes engine tests as technology changes.  Categories E2, E3 and E5 were recently delisted and E9 was added in 2008 for Euro 5 generation of engines.

A summary of the Series E Heavy-duty Diesel categories follows:

E4 Specifies stable, stay-in-grade oil providing further control of piston cleanliness, wear, soot handling, and lubricant stability compared to E3. It is recommended for highly rated diesel engines meeting Euro 1, Euro 2, Euro 3, Euro 4 and Euro 5 emission requirements and running under very severe conditions; e.g. significantly extended oil drain intervals according to the manufacturer’s recommendations.

E6 Stable, stay-in-grade oil that provides control of piston cleanliness, wear, soot handling and lubricant stability.  Recommended for highly rated diesel engines meeting Euro 1, Euro 2, Euro 3, Euro 4 and Euro 5 emission requirements and running under very severe conditions, e.g. significantly extended oil drain intervals according to the manufacturer’s recommendations.  Suitable for EGR engines, with or without particulate filters and is also for engines fitted with SCR NOx reduction systems.  E6 quality is strongly recommended for engines fitted with particulate filters and is designed for use in combination with low sulfur diesel fuel (max 50 ppm).  This oil has SAPS requirements.  It requires a maximum of 1% sulfated ash and less than 0.08% phosphorus and less than 0.3% sulfur. 

E7 Stable, stay-in-grade oil providing effective control with respect to piston cleanliness and bore polishing.  It provides excellent wear and turbocharger deposit control, soot handling and lubricant stability.  It is recommended for highly rated diesel engines meeting Euro 1, Euro 2, Euro 3, Euro 4 and Euro 5 emission requirements and running under severe conditions, e.g. extended oil drain intervals according to the manufacturer’s recommendations.  It is suitable for engines without particulate filters and for most EGR engines and most engines fitted with SCR NOx reduction systems.  It has no SAPS limit for the oil and allows a maximum of 2.0% sulfated ash.