American Power Group Corporation announced recent upgrades to the S4000 Turbocharged Natural Gas® dual fuel system. The new Variable Fuel Management (“VFM”) software upgrade allows oil and gas drillers to adjust their specific site’s dual fuel mapping calibrations to optimize performance for four different natural gas compositions including CNG, LNG, and two BTU levels of field gas including up to 1,450 BTU. This software upgrade helps to better match the source gas to the corresponding dual fuel optimization table. S4000 customers are experiencing up to a 10% improved diesel substitution rate which substantially improves their payback period, which is currently in the 6 to 9 month range depending on the source gas. The VFM upgrade is in addition to recent display upgrades and new telematics remote monitoring capabilities.