Lubricant Impact on Friction by Engine Component: A Motored Friction Tear Down Assessment of a Production 3.6L Engine 2019-01-2239

Worldwide, Fuel Economy (FE) legislation increasingly influences vehicle and engine design, and drives friction reduction. The link between lubricant formulation and mechanical friction is complex and depends on engine component design and test cycle. This Motored Friction Tear Down (MFTD) study characterizes the friction within a 3.6L V6 engine under operating conditions and lubricant choices relevant to the legislated FE cycles. The high-fidelity MFTD results presented indicate that the engine is a low-friction engine tolerant of low viscosity oils. Experiments spanned four groups of engine hardware (reciprocating, crankshaft, valvetrain, oil pump), five lubricants (four candidates referenced against an SAE 0W-20) and five temperature regimes. The candidate lubricants explored the impact of base oil viscosity, viscosity modifier (VM) and friction modifier (FM) content. The results indicate that (i) a prototype SAE 0W-8 fluid generated the largest overall reduction in friction, (ii) the valvetrain group responded well to FM content, and (iii) an SAE 0W-20 with alternative VM performed remarkably well at low temperatures (-7°C to 30°C). In order to understand the significance of that engine friction reduction at the overall vehicle level, the data was used to compare energy usage predictions of a mid-size crossover Sport Utility Vehicle (SUV) equipped with the studied engine over the FTP75 and HWFET legislative cycles. In those simulations, the SAE 0W-8 indicated a potential energy usage reduction of 1.1% and 0.8% over the FTP75 and HWFET, respectively. This collaborative project illustrates how (i) engine components’ contributions vary significantly with operating conditions, (ii) optimal fluid formulations differ among engine components and cycles, challenging final formulation choice, and (iii) a co-engineered design of hardware and fluid components could assist Original Equipment Manufacturers (OEMs) in meeting legislative FE targets.