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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 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.

Gasoline direct-injection (GDI) engines have a well-known propensity to form intake valve deposits (IVD), regardless of operator service, engine architecture, or cylinder configuration. Due to the lack of a fuel-washing process that is typical of Port Fuel Injected (PFI) engines, the deposits steadily accumulate over time and can lead to deterioration in combustion, unstable operation, valve-sticking, or engine failure. Vehicles using these engines are often forced to undergo expensive maintenance to mechanically remove the deposits, which eventually re-form. The deposit formation process has not been well-characterized and there is no standardized engine test to study the impact of fuel or lubricant formulation variables. To meet this need, a proprietary vehicle-based GDI-IVD test that is both repeatable and responsive to chemistry has been developed.

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.

The traditional vehicle-based approach to measuring the effect of oil-related fuel economy has relied on separate oil-aging and measurement processes where oil-aging takes place using an established driving protocol like the EPA Approved Mileage Accumulation (AMA) Driving Schedule for vehicle aging, then at set mileage intervals fuel economy is assessed using procedures such as the EPA FTP75 and Highway Fuel Economy emission test protocols described in 40 CFR, Parts 86 and 600. These test methods are useful for producing discrete snapshots of fuel economy at set mileage intervals but are unable to provide continuous information about oil-related changes in fuel economy. During the tests, the vehicle's fuel economy is indirectly calculated using a carbon-balance method of the bagged sample of dilute tailpipe emissions that effectively integrates the fuel economy of the vehicle during the sample interval which varies between eight and fifteen minutes.

A host of bench and engine tests have historically been used by formulators to assess fuel economy when developing engine oils for gasoline-powered passenger cars and light trucks. Some of these methods assess basic lubricant physical properties such as hydrodynamic, boundary and thin-film friction, and are useful for quickly screening experimental components and formulations. Some methods assess rotational drag of a motored engine and offer insights into the friction of various engine parts. Still other methods directly measure the energy consumption in a test engine running in a research laboratory and thus come the closest to simulating a consumer-operated vehicle. Each test method has inherent limitations and is based on underlying assumptions, producing artifacts that must first be understood and then analyzed for relevance to either industry lubricant specifications or real world fuel economy performance.

Previous research to understand the mechanism for piston deposit formation in the Sequence IIIG engine test has focused on characterizing the piston deposits. These studies concluded that, in addition to lubricant derived materials, Sequence IIIG piston deposits contain a significant amount of fuel-derived carbonaceous material. The presence of fuel degradation by-products in Sequence IIIG deposits shows that blow-by is a significant contributor to deposit formation. However, blow-by can either assist in the degradation of the lubricant or can simply be a source for organic material which can be incorporated into the deposits. Therefore, a series of modified Sequence IIIG engine tests were conducted to better determine the effect of blow-by on deposit formation. In these studies deposit formation on different parts of the piston assembly were examined since different parts of the piston assembly are exposed to different amounts of blow-by.

In the next ILSAC passenger car motor oil specification the Sequence IIIG engine test, as well as two versions of the Thermo-Oxidation Engine Oil Simulation Test (TEOST) have been proposed as tests to determine the ability of crankcase oils to control engine deposits. The Sequence IIIG engine test and the TEOST MHT test are designed to assess the ability of lubricants to control piston deposits and the TEOST 33 test is designed to assess the ability of lubricants to control turbocharger deposits. We have previously characterized the chemical composition of Sequence IIIG piston deposits using thermogravimetric, infrared and SEM/EDS analyses. Sequence IIIG piston deposits contain a significant amount of carbonaceous material and the carbonaceous material is more prevalent on sections of the pistons that should encounter higher temperatures. Furthermore, the carbonaceous material appears to be a deposit formed by the Sequence IIIG fuel.

The poisoning of three way catalysts (TWC) by the phosphorus contained in oil formulations containing zinc dialkyldithiophosphate (ZDDP) is examined. Catalysts were exposed to various types of ZDDP and detergents under conditions that were known to reduce performance through phosphorus poisoning without the blocking of sites by formation of glazing. The presence of phosphorus was detected with energy dispersive x-ray spectroscopy (EDX). In addition to analyzing the surface concentration of the phosphorus on the washcoat, the catalyst was cross cut so phosphorus that diffused into the washcoat could be mapped. The total phosphorus in the catalyst could then be calculated. The amount of total phosphorus detected correlated well with the reduced activity of the catalyst as measured by the temperature of 50% conversion.

An engine test has been developed to assess the impact of volatile phosphorus from passenger car engine oils on catalytic converter efficiency. The ten-day, steady-state, catalyst aging test was established to promote the production and consumption of volatile phosphorus species contained in crankcase vapors that are evacuated and combusted via the PCV system. A system for sampling, analyzing and identifying crankcase vapors led to a greater understanding of the phosphorus-based poisoning mechanism. Catalytic converter conversion efficiency was assessed through an engine-based system that swept catalyst inlet temperature from low to high while using a constant flow of controlled exhaust gas. The test results indicate correct ranking of field-tested oils that have catalyst poisoning data.

In-use vehicle regional inspection and maintenance (I/M) programs in the United States (US) and Canada generate a tremendous volume of data that provides a means for evaluating vehicle emissions compliance in actual consumer use. In this study, IM240 test data for several 1996 to 2001 vehicle models are analyzed from different regional programs in the US and Canada to confirm the suitability of using these data for evaluation of vehicles equipped with advanced emission control technology and to examine the various potential factors responsible for emissions noncompliance. Relative comparisons between US and Canadian program data are made for vehicle models used in the Alliance of Automobile Manufacturers (AAM) MMT® Test Program to examine the potential impact of differences in fuel properties on consumer experience and vehicle compliance.

Emissions regulations for 2007 will likely require engine manufacturers to use a diesel particulate filter (DPF) to meet particulate matter (PM) emission requirements. With the lower operating temperatures of light-duty diesel engines, some form of catalyst will be required to facilitate oxidation of accumulated soot PM to regenerate the DPF. This catalyst can either be permanently applied to the filter substrate in the manufacturing process, or be continuously delivered via the diesel fuel. In this study we examined the impact of using both forms of catalyst. A recently published study of the fuel-borne catalyst additive MMT [1] (Methylcyclopentadienyl Manganese Tricarbonyl), reviewed the performance of MMT in conjunction with an uncatalyzed DPF [2].

Control and elimination of mobil-source particulate matter (PM) emissions is of increasing interest to engineers and scientists as regulators in industrialized countries promulgate lower emission levels in diesel engines. Relative to their gasoline engine counterparts, today's diesel engines, in general, still emit a higher mass of PM. While strictly speaking, this PM is an agglomeration of organic and inorganic particles, the predominant component is carbon and is commonly referred to as “soot”. For mobil-source PM control, one of the current preferred technologies is the ceramic closed-cell monolith Diesel Particulate Filter (DPF). Ideally, DPFs accumulate and store PM during low speed/temperature engine operation and burn the accumulated PM during high speed/temperature operation.

SAE Paper 2002-01-2894 entitled, “The Impact of MMT Gasoline Additive on Exhaust Emissions and Fuel Economy of Low Emission Vehicles (LEV)” presents discussion and conclusions concerning the emissions from vehicles that accumulated mileage on gasoline with and without the fuel additive, methylcyclopentadienyl manganese tricarbonyl (or MMT®). Although the authors of the paper express concern about use of MMT®, the data on which the authors rely are consistent with the results and conclusions from prior evaluations of MMT® which have found that MMT® is compatible with effective emission control system operation (1,2,3). All vehicles tested in the study met the emission standards for all pollutants that apply to the test vehicles in-use and analysis of the data show MMT® had no effect on fuel economy.

The effects of the cetane improvers* 2-ethylhexyl nitrate (EHN) and di-tertiary-butyl peroxide (DTBP) on regulated exhaust emissions from a 1993 Detroit Diesel Series 60 heavy-duty diesel engine were studied. EHN and DTBP were added to two commercially available fuels at concentrations ranging from 500 to 12,000 ppm by volume. Both additives reduced CO, NOx, and particulate emissions as measured in the hot start portion of the FTP heavy-duty transient emissions cycle. A comparison of the emissions response of the two additives shows that the nitrogen in EHN does not contribute to NOx emissions at typical treat rates.