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In view of CO2 reduction, aimed to mitigate global warming, Fuel Economy (FE) is gaining a primary role in new specifications for engine lubricating oils. Not only oil rheological properties and friction reducer additives, but also all the components of the formulation, such as basestocks, viscosity modifier and additive package, are involved in achieving FE performances. Tribological tests were carried out in our labs to investigate the effect of detergent additives: in particular, the positive role of detergents based on Calcium salts ofcalixarenes, cyclic oligomers obtained from reaction of p-functionalized phenols with formaldehyde, emerged. This type of additives is particularly suitable for modern lubricants preserving aftertreatment efficiency as they are sulfur-free.

The present work, carried out within the framework of the JOULE-3 European joint project entitled “Fuel and lubricant formulations for high de-polluted engines”, investigates the effect of both the fuel and the lubricating oil quality on deposits, wear and exhaust emissions in the presence of a high EGR rate, with specific attention to the emission variation during aging. Two fuels (a current Italian typical fuel and a Swedish high quality fuel) and two lubricants (a traditional mineral oil SAE 15W-40/ACEA B2 and a full synthetic SAE 0W-40/ACEA B3) were used to carry out six tests, each one characterized by 126-hour duration at different running conditions, on a VM Turbotronic Diesel engine. The engine evaluation pointed out an interaction between oil and fuel: if the high quality fuel (nearly zero S) is used, a low level of cylinder bore polishing and top ring wear, weakly affected by the oil quality, occurs.