Petrol v Diesel

We're fairly new to caravanning and tow with a 113 BHP Kia Ceed we have a Lunar 2 berth 1150 MTPLM and so far no problems it seems a suitable match but we have decided we want a Mondeo estate and can't decide which engine to buy it's going to be a 1.6 but do we go for the petrol with 163 BHP 44 mpg or the diesel with 115 BHP 65 mpg and it will be a manual gearbox,we do around 12,00 miles annualy including we think around 2,000 towing caravan going for the 1.6 engine for better economy don't realy want a 2.0