A Consolidated Investigation on LPG as an Alternative Fuel for Public Utility Jeepneys

This paper presents the results of a two-phase Philippine study to determine the actual mileage (km/liter) of in-use diesel and LPG (liquefied petroleum gas or Auto-LPG) public utility jeepneys plying two separate Metro Manila urban routes using both on-road and chassis dynamometer tests. Measured average load factor in on-road tests was 60-70%. Dynamometer tests at 100% load factor utilized drive cycles derived from on-road speed data. A “diesel equivalent mileage” of actual LPG mileage, deemed indicative of LPG “fuel energy conversion efficiency” relative to diesel, was calculated (based solely on fuel heating values and densities) for comparing actual mileage from both fuels. The LPG actual mileage in both on-road and laboratory tests was lower than diesel mileage. In on-road tests, the LPG actual mileage was lower than diesel actual mileage by about the same percentage LPG heating value was lower than diesel’s per liter of fuel. The LPG diesel equivalent mileage was also about the same as diesel actual mileage so that fuel conversion efficiencies of both jeepney types were deemed similar. In chassis dynamometer tests at 100% load factor, the LPG diesel equivalent mileage was lower than diesel actual mileage. This implied that in addition to the effect of lesser LPG heating value per liter, the LPG jeepneys had lower energy conversion efficiencies than diesel at load factors higher than experienced in the on-road tests. Optimization of the LPG jeepney via tuning and/or powertrain configuration is suggested especially if deployed at higher load factors. The amount of financial incentives, e.g. fuel pricing, to promote LPG jeepneys should take into account its comparable on-road fuel conversion efficiency to diesel and generally accepted better emissions.