Euro 5 - 3 litre manual - likely mpg?

Evening all, we're in process of buying a new motorhome, Fiat Ducato Maxi Chassis, Euro 5 type, 3 litre engine with a manual gearbox. Just wondering what type of economy we're likely to get from it. I know it'll depend somewhat on what our payload is etc, but thought we'd see if anyone can give any approximate idea on mpg. Thanks and Happy Motorhoming!