Been tracking the kms i get from LPG.

I get between 350 and 500kms from around 65L. Its hard to say how much fuel I use because 'full' is dependent on how much I drain from the tank and how much it decides to put back in before it clicks off.

Highway usage gets much better results - usually below 15/100 from the trip computer.
around the 'burbs gets me over 20/100.

After speaking to a good mechanic mate (A good mechanic more than a good mate) I have changed my LPG/Petrol usage habits so I no longer get measurable results.

Turns out, little bits of petrol all the time rather than 10-20L of petrol after a whole tank of gas is better on the engine...