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Engine oil plays an important role in improving fuel economy of vehicles by reducing frictional losses in an engine. Our previous investigation explored the friction reduction potential of next generation engine oils by looking into the effects of friction modifiers and dispersant Inhibitor packages when engine oil was fresh. However, engine oil starts aging the moment engine start firing because of high temperature and interactions with combustion gases. Therefore, it is more relevant to investigate friction characteristics of aged oils. In this investigation, oils were aged for 5000 miles in taxi cab application.

The oil and additive industry is challenged to meet future automotive legislations aimed at reducing worldwide CO2 emissions levels. The most efficient solution used to date has been to decrease oil viscosity leading to the introduction of new SAE grades. However this solution may soon reach its limit due to potential issues related to wear with lower engine oil viscosities. In this paper, an innovative solution is proposed that combines the use of a new tailor-made polyalkylene glycol (PAG) with specific anti-wear additives. Valvetrain wear measurements using radionuclide technique demonstrates the robustness of this solution. The wear performance was also confirmed in Sequence IVA test. An extensive tribological evaluation (film formation, wear and tribofilm surface analysis) of the interactions between the base oil and the anti-wear additives lead us to propose an underlying mechanism that can explain this performance benefit.

Deposit formation within turbocharger compressor housings can lead to compressor efficiency degradation. This loss of turbo efficiency may degrade fuel economy and increase CO2 and NOx emissions. To understand the role that engine oil composition and formulation play in deposit formation, five different lubricants were run in a fired engine test while monitoring turbocharger compressor efficiency over time. Base stock group, additive package, and viscosity modifier treat rate were varied in the lubricants tested. After each test was completed the turbocharger compressor cover and back plate deposits were characterized. A laboratory oil mist coking rig has also been constructed, which generated deposits having the same characteristics as those from the engine tests. By analyzing results from both lab and engine tests, correlations between deposit characteristics and their effect on compressor efficiency were observed.

The application of polyalkylene glycol (PAG) as a base stock for engine oil formulation has been explored for substantial fuel economy gain over traditional formulations with mineral oils. Various PAG chemistries were explored depending on feed stock material used for manufacturing. All formulations except one have the same additive package. The friction performance of these oils was evaluated in a motored single cylinder engine with current production engine hardware in the temperature range 40°C-120°C and in the speed range of 500 RPM-2500 RPM. PAG formulations showed up to 50% friction reduction over GF-5 SAE 5W-20 oil depending on temperature, speed, and oil chemistry. Friction evaluation in a motored I-4 engine showed up to 11% friction reduction in the temperature range 40°C-100°C over GF-5 oil. The paper will share results on ASTM Sequence VID fuel economy, Sequence IVA wear, and Sequence VG sludge and varnish tests. Chassis roll fuel economy data will also be shared.

In an internal combustion engine, the wear in the piston ring/cylinder bore contact initially increases rapidly due to run-in and then attains a steady state during which the engine spends most of its useful life. This paper describes the development of an abrasive wear model for both cylinder bore and piston rings for the steady state period. The model took into account shear thinning of the lubricant, but it did not consider the effects of transient operations, geometry changes due to bore distortions, ring twist, ring motion, and corrosion. The model predicted the bore wear depth distribution from the top dead center (TDC) to the bottom dead center (BDC) and ring wear depth under different operating conditions. The maximum bore wear depth was predicted to occur at about 20 degrees after TDC where the combustion gas pressure reached its peak value. The model predicted an increase in bore and ring wear depth with increasing engine speed.