you're right that blending conventional diesel fuel with NG is not a new concept. that's the "what". Westport's High Pressure Direct Injection (HPDI) is the "how" & the "how much". most of the so called competion uses a mixer valve to blend NG with the intake air and use between 30-70% NG. HPDI uses 95% NG. As such, the fuel cost difference is very significant.