Thing that comes up here is the word " diesel". In the US you have regulations that make many Commercial operations non viable , so operators go back to Petrol ( Gas) trucks. As I said, that is not even considered as an option outside the US. So we are talking about two very different scenarios when we are talking Motorhome Fuel Economy. It is interesting to see your posts compared to the FB site I posted. Yes many it seems here are getting poor fuel economy with Diesel, but the Gas options you refer to, are non- existent outside NA, although there have been LPG conversions of Ford V10 engines