Nissan LPG

First, you need to put Nissan's attitude to running its cars on LPG into context. Nissan doesn't design or test its cars on LPG, so it has no knowledge of the impact of doing so. If they supported changing to LPG Nissan would, in effect, be taking on the responsibility for what might happen should you convert to LPG, so they advise against it. It's actually got little to do with whether or not their cars would happily run on LPG or not. The problem you will have is finding a certified kit for the conversion. Because of the low demand for converting the Maxima kits haven't been developed.