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Liquefied petroleum gas (LPG) is commonly known as autogas when used as a fuel for internal combustion engines. In North America, autogas primarily consists of propane, but can contain small amounts of butane, methane and propylene. Autogas is not a new fuel for internal combustion engines, but as engine technology evolves, the properties of autogas can be utilized to improve engine and vehicle efficiency. With support from the Propane Education & Research Council (PERC), Southwest Research Institute (SwRI) performed testing to quantify efficiency differences with liquid autogas direct injection in a modern downsized and boosted direct-injected engine using the production gasoline fuel injection hardware. Engine dynamometer testing demonstrated that autogas produced similar performance characteristics to gasoline at part load, but could be used to improve brake thermal efficiency at loads above 9 bar Brake Mean Effective Pressure (BMEP).

In June of 2015, the Environmental Protection Agency and the National Highway Traffic Safety Administration issued a Notice of Proposed Rulemaking to further reduce greenhouse gas emissions and improve the fuel efficiency of medium- and heavy-duty vehicles. The agencies proposed that vehicle manufacturers would certify vehicles to the standards by using the agencies’ Greenhouse Gas Emission Model (GEM). The agencies also proposed a steady-state engine test procedure for generating GEM inputs to represent the vehicle’s engine performance. In the proposal the agencies also requested comment on an alternative engine test procedure, the details of which were published in two separate 2015 SAE Technical Papers [1, 2]. As an alternative to the proposed steady-state engine test procedure, these papers presented a cycle-average test procedure.

The performance and projected longevity of a representative mineral-oil based CI-4 lubricant was evaluated using seven early production heavy-duty diesel engines tested under laboratory conditions. The 2003-2004 model year engines span the range from 5.9L to 15.2L and include engines with and without cooled EGR. All engines were evaluated using the same engine dynamometer cycle, fuel, and lubricant. The test cycle was based on the AVL 8-mode points, run as an 8-hour cycle, which stressed the oil with extended periods of operation ranging from idle to high load, but overall was considered a relatively low severity cycle. Oil analysis results display engine-to-engine differences in the rates of viscosity change, fuel dilution, soot accumulation, wear metal accumulation, total base number depletion, and oxidation.