The big mpg killers are driving in town, roads which have many bends and speed limit changes and, despite what many will tell you, use of aircon. Our little car which does ~50mpg or more in normal conditions can't even reach 45mpg with auto aircon in the baking hot conditions we currently have. The general reason that cars get better mpg coming back is that they don't have to contend with starting from cold and the higher fuel consumption that results. My Karoq has done nearly 3000 miles according to the long term computer, at 49.8 mpg, and on the continent last month, when it was hot enough to crack our windscreen, we were getting 52 mpg even with the aircon running. Our best recorded figure on a trip, all be it a short journey, was over 80 mpg. About 10 miles, aircon off, about 940 feet drop in elevation.