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There has been a global technology convergence by engine manufacturers as they strive to meet or exceed the ever-increasing fuel economy mandates that are intended to mitigate the trend in global warming associated with CO2 emissions. While turbocharging and direct-injection gasoline technologies are not new, when combined they create the opportunity for substantial increase in power output at lower engine speeds. Higher output at lower engine speeds is inherently more efficient, and this leads engine designers in the direction of overall smaller engines. Lubricants optimized for older engines may not have the expected level of durability with more operating time being spent at higher specific output levels. Additionally, a phenomenon that is called low-speed pre-ignition has become more prevalent with these engines.

When gasoline-fueled vehicles are operated in consumer service, the oil used to lubricate the engine plays a key role in engine cooling, reducing friction, maintaining efficient operation, and optimizing fuel economy. The effects of normal vehicle operation on oil deterioration have a direct impact on fuel consumption. The authors have observed substantial differences between the deterioration of engine oil and resulting fuel economy under real-world driving conditions, and the deterioration of oils and resulting fuel economy in the standard laboratory test used to assess fuel economy in North America, the Sequence VID engine test (ASTM D7589). By analyzing the data from vehicles and comparing these data to the Sequence VID the authors have proposed and evaluated several changes to the Sequence VID test that improve the correlation with real-world operation and improve test discrimination.

Improving vehicle fuel efficiency is a key market driver in the automotive industry. Typically lubricant chemists focus on reducing viscosity and friction to reduce parasitic energy losses in order to improve automotive fuel efficiency. However, in a transmission other factors may be more important. If an engine can operate at high torque levels the conversion of chemical energy in the fuel to mechanical energy is dramatically increased. However high torque levels in transmissions may cause NVH to occur. The proper combination of friction material and fluid can be used to address this issue. Friction in clutches is controlled by asperity friction and hydrodynamic friction. Asperity friction can be controlled with friction modifiers in the ATF. Hydrodynamic friction control is more complex because it involves the flow characteristics of friction materials and complex viscosity properties of the fluid.

Low speed pre-ignition (LSPI) is an undesirable combustion phenomenon that limits the fuel economy, drivability, emissions and durability performance of modern turbocharged engines. Because of the potential to catastrophically damage an engine after only a single pre-ignition event, the ability to reduce LSPI frequency has grown in importance over the last several years. This is evident in the significant increase in industry publications. It became apparent that certain engine oil components impact the frequency of LSPI events when evaluated in engine tests, notably calcium detergent, molybdenum and phosphorus. However, a close examination of the impact of other formulation additives is lacking. A systematic evaluation of the impact of the detergent package, including single-metal and bimetal detergent systems, ashless and ash-containing additives has been undertaken using a GM 2.0L Ecotec engine installed on a conventional engine dynamometer test stand.

Countries from every region in the world have set aggressive fuel economy targets to reduce greenhouse gas emissions. To meet these requirements, automakers are using combinations of technologies throughout the vehicle drivetrain to improve efficiency. One of the most efficient types of gasoline engine technologies is the turbocharged gasoline direct injection (TGDI) engine. The market share of TGDI engines within North America and globally has been steadily increasing since 2008. TGDI engines can operate at higher temperature and under higher loads. As a result, original equipment manufacturers (OEMs) have introduced additional engine tests to regional and OEM engine oil specifications to ensure performance of TGDI engines is maintained. One such engine test, the General Motors turbocharger coking (GMTC) test (originally referred to as the GM Turbo Charger Deposit Test), evaluates the potential of engine oil to protect turbochargers from deposit build-up.

There has been a trend in the automotive industry toward the use of lower viscosity engine oils as fuel economy requirements become more demanding across the globe. Lower viscosity fluids may improve fuel economy due to their improved pumpability, lower churning losses, and thinner lubricating films. However, there is one important caveat related to the use of these fluids: the amount of improvement, if any, is hardware design and application dependent. Standard industry fuel economy tests and engines with differing designs may show divergent responses when using lower viscosity engine oils, not always showing an improved fuel economy response. This paper summarizes the work conducted by the authors to demonstrate how and why the inconsistent results in fuel economy can occur with low viscosity oils.

There is still a need in the industry for engine oils that have low viscosities to improve vehicle fuel efficiency but also protect engines from wear. Viscosity modifiers (VMs) are chief additives responsible for adjusting the viscometric characteristics of automotive lubricants. Most notably, VMs have a significant impact on a lubricant's viscosity-temperature relationship as indicated by viscosity index (VI), cold cranking simulator (CCS) viscosity, and high temperature high shear (HTHS) viscosity of engine oils. Functional copolymers bearing branched, linear, or anti-wear functionalities have been synthesized and evaluated for viscometric and wear protection performance. The resulting polymers improved tribofilm formation, shear stability and CCS viscosities. Indirect benefits including Noack improvement and trim oil reduction were observed.

Since the mid-1990's, original equipment manufacturers (OEMs) of automobiles have been implementing torque converter clutches in automatic transmissions with a continuous, controlled slip mode, in order to improve the fuel economy of their vehicles. These Continuously Slipping Torque Converter Clutches (CSTCCs) are prone to an undesirable phenomenon commonly called shudder. This phenomenon has been attributed to specific shapes or slopes in the friction coefficient versus sliding speed curve of the fluid/clutch interface. Here, a method is explained that was developed to be able to screen fluids for shudder tendency, both in fresh and used states. Also included is a description of the reason for implementing CSTCCs, some background on shudder, and supporting data showing how the test method can distinguish between fluids that have different shudder tendencies.

A vehicle fleet of seven low-mileage gasoline direct injection (GDI) vehicles from the U.S. market were tested to determine if GDI injector deposits were present causing a loss in fuel economy (FE). The real-world vehicles were tested “as-is” from the field. The data shows that, even in a deposit control additive (DCA) mandated market that uses E10 gasoline, injector deposits can still result in up to 2.7 % loss in FE. In addition, the data shows that the level of real-world FE loss is comparable to that demonstrated in the GDI injector fouling test developed to simulate real-world dirty-up of GDI vehicle injectors.

Modern light-duty trucks and SUV's are designed to be aerodynamic to increase fuel economy. Such vehicle design significantly reduces the amount of air available to cool the rear axle in rear wheel drive vehicles. Reduced cooling coupled with higher power output and additional load from trailer towing operations results in higher axle operating temperatures, especially during the early operation or “break-in” phase of axle life. Higher axle operating temperatures decrease oil viscosity resulting in reduced oil film formation ability to protect against wear and contact fatigue. High temperature also shortens the useful life of gear oils. To facilitate the development of gear oils capable of reducing axle operation temperature, we have developed a laboratory simulation test method that can closely simulate actual trailer-towing driving on Baker's grade road under maximum GVCWR of close to 6,033 kg (13,300 lbs).