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Chassis dynamometer tests are often used to determine vehicle fuel economy (FE). Since the entire vehicle is used, these methods are generally accepted to be more representative of ‘real-world’ conditions than engine dynamometer tests or small-scale bench tests. Unfortunately, evaluating vehicle fuel economy via this means introduces significant variability that can readily be mitigated with engine dynamometer and bench tests. Recently, improvements to controls and procedures have led to drastically improved test precision in chassis dynamometer testing. Described herein are chassis dynamometer results from five fully formulated engine oils (utilizing improved testing protocols on the Federal Test Procedure (FTP-75) and Highway Fuel Economy Test (HwFET) cycles) which not only show statistically significant FE changes across viscosity grades but also meaningful FE differentiation within a viscosity grade where additive systems have been modified.

Fuel economy is not an absolute attribute, but is highly dependent on the method used to evaluate it. In this work, two test methods are used to evaluate the differences in fuel economy brought about by changes in engine oil viscosity grade and additive chemistry. The two test methods include a chassis dynamometer vehicle test and an engine dynamometer test. The vehicle testing was conducted using the Federal Test Procedure (FTP) testing protocol while the engine dynamometer test uses the proposed American Society for Testing and Materials (ASTM) Sequence VIE fuel economy improvement 1 (FEI1) testing methodology. In an effort to improve agreement between the two testing methods, the same model engine was used in both test methods, the General Motors (GM) 3.6 L V6 (used in the 2012 model year Chevrolet™ Malibu™ engine). Within the lubricant industry, this choice of engine is reinforced because it has been selected for use in the proposed Sequence VIE fuel economy test.

Dual fuel engines have shown significant potential as high efficiency powerplants. In one example, SwRI® has run a high EGR, dual-fuel engine using gasoline as the main fuel and diesel as the ignition source, achieving high thermal efficiencies with near zero NOx and smoke emissions. However, assuming a tank size that could be reasonably packaged, the diesel fuel tank would need to be refilled often due to the relatively high fraction of diesel required. To reduce the refill interval, SwRI investigated various alternative fluids as potential ignition sources. The fluids included: Ultra Low Sulfur Diesel (ULSD), Biodiesel, NORPAR (a commercially available mixture of normal paraffins: n-pentadecane (normal C15H32), and n-hexadecane (normal C16H34)) and ashless lubrication oil. Lubrication oil was considered due to its high cetane number (CN) and high viscosity, hence high ignitability.

Southwest Research Institute (SwRI) converted a Cummins ISX 12 G in-line six-cylinder engine to a Dedicated EGRTM (D-EGRTM) configuration. D-EGR is an efficient way to produce reformate and increase the EGR rate. Two of the six cylinders were utilized as the dedicated cylinders. This supplied a nominal EGR rate of 33% compared to the baseline engine utilizing 15-20% EGR. PFI injectors were added to dedicated cylinders to supply the extra fuel required for reformation. The engine was tested with a high energy dual coil offset (DCO®) ignition system. The stock engine was tested at over 70 points to map the performance, 13 of these points were at RMC SET points. The D-EGR converted engine was tested at the RMC SET points for comparison to the baseline. The initial results from the D-EGR conversion show a 4% relative BTE improvement compared to the baseline due to the increased EGR rate at 1270 rpm, 16 bar BMEP.