On my (now sold) Insight CVT, I coasted in neutral until the instant fuel economy bar dropped below 150 MPG. The reading was consistently 16 MPH, so I just use 16/150 for idle fuel consumption.
Works out to just under .12 GPH at idle.
I think but cant prove the VX is very close to that becasue it idles at about 450 RPM, lowest idle speed of any car I have owned except my 37 Ford flathead V8 which idled at 350 RPM.
The Insight will average 40 mph on the same fuel an average V8 consumes idling with no electrical accessory loads.
I once tried to measure idle consumption on my brothers 90 Civic, with a DVOM on the fuel tank sending unit. When the tank level actually read that it had INCREASED, I realized that the heat conducted by the fuel and the ambient temperature increase had made the fuel in the tank expand, which was the cause of his magic Honda that made fuel while running
.
regards
Mech