Welcome to iRV2.
The newer Ford engines are regular gas for fuel .
Your mileage will vary, road conditions , SPEED, weight and wind.
MPG, can change by 20% between drivers with the same RV.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.