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A standardized test to evaluate engine performance, durability and oil life was conducted on a 10.3 liter 3176B Caterpillar diesel pilot ignition natural gas “dual fuel” engine. The testing was performed at the Caterpillar Technical Center in Mossville, Illinois. The engine durability evaluation included engine disassembly with both dimensional and visual inspection of key components. Engine performance was monitored throughout the test and oil analysis was performed at regular intervals. The technical results support the conclusion that engine life and oil life of a dual fuel (natural gas) engine will meet or exceed typical diesel values and that engine performance will remain within factory specified limits for the life of the engine.

The standard procedure for determining non-methane hydrocarbon (NMHC) emissions is to subtract measured methane emissions from total hydrocarbon emissions measured by flame ionization detector. The results of this method were compared to the results of direct GC speciation of hydrocarbon emissions. For gasoline vehicles using an all-hydrocarbon fuel, the two methods demonstrate nearly perfect correlation, with a linear regression coefficient near 1.0, and R2 = 0.999. The correlation using reformulated gasoline is only slightly worse. For natural gas vehicles, however, the correlation was poor, with R2 < 0.30. This poor correlation is attributed to the high methane content of natural gas, which results in NMHC emissions being very low compared to the level of methane. Both the total hydrocarbon and methane measurements contain some error, and the resulting combined error in the NMHC concentration is of the same order as the concentration itself.