hello, i just bought a fairlane ghia 2005. the car runs pretty good both on petrol and lpg. but the problem is that it does not change to lpg sometimes. I went through several blogs and all i can get is that the engine has to be heated up for the change. i drive pretty fast and put a lot of pressure on the engine. for an example I went from lakemba to auburn (roughly 15 km) the fuel changed into lpg. but yesterday i went to campbelltown (45 km) with an average speed of 140; still it didn't change to lpg. Please help,,,

what type of LPG system does it have? & what name does it go by

stargas. And I'm not sure what the problem is.. It runs good with lpg as well but sometimes does not change to lpg. It seems like the car has its own wish to change to lpg. what should I do?? please suggest