Evolution of the Additive Technology for Top Tier Lubricating Oils : the Use of Calixarene Detergents for Fuel Economy Improvement

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 many other components of the formulation, such as basestocks, viscosity modifier and additive package, are involved in improving FE performances. Tribological tests were carried out to investigate the effect of detergent additives: in particular, both Eni proprietary 400 TBN and 150 TBN Calcium calixarene-based detergents, were evaluated in MTM tribotest where a lower friction coefficient curve in boundary regime was achieved in comparison to traditional detergents. Also in SRV tribo tests the good effect of calixarenes was proven. A preliminary engine test evaluation on Sequence VIE provided a further confirmation of the good behavior of calixarene-based detergents jointly with an amino-type friction reducer: a FE result with a pass margin of 30% against ILSAC GF-6A limit for SAE 0W-20 was achieved with the use of a fully calixarene detergent system; the use of calixarene OB detergent in combination with other detergent types (as Magnesium OB and neutral Calcium sulfonates), provided a slightly lower performance but despite this, it was considered more oriented to the performance requirements of current specifications, and used in M111FE tests where the SAE 0W-20 oil provided over 4% FE improvement, with a margin of 35% from ACEA C5 limit, while both 5W-30 at low (2.9 Pa.s) and high (3.5 Pa.s) HTHSv fulfilled the ACEA C2 limit of 2.5%. The same oils showed robust FE performances on chassis-dyno tests according to NEDC cycle. Finally, the mixed detergent system fulfilled all the other traditional oil performances, as well as emerging issues like low speed pre-ignition and air entrainment, required by the current specifications.