I owned my cruiser for 10 years now and have been getting just over 8 km/lt (22mpg) on a M'way run on Petrol and about 7 km/lt (20mpg) doing same journey on LPG.
Around town , this goes down to around 6 km/lt (17mpg) on Petrol and 5.5 km/lt (15mpg) on LPG.
These figures have been pretty consistent for years, with only (very) small variations due to seasons/weather.