When I bought my xf in September I was immediately impressed with the fuel consumption but this has dropped off recently by rather a lot.

Same journey

Same style of driving
Is battery decay a possibility ?

 

Unless you cleared user settings when you purchased the vehicle, the first readings will have been the calculated from the PO's driving style whereas the current ones are derived from your driving style.

Graham

 

I changed to a new trip and reset it. My driving style was better.

 

Jaguar always give the warning regarding the trip computer "the displayed information is for guidance only, as it can be affected by traffic, road and weather conditions."

Before chasing a possible fault, I'd do an actual consumption calculation from fuel fill to refill.

Graham

 

Yep. Do the actual fuel calculation when topping up the fuel. Every make and model vehicle I have owned has a computer that errs 1.5-2 mpg to the better than actual fuel mileage (assuming odometers are accurate). I've also found that tire air pressure has an impact along with wind and outside air temperature. Colder weather means the engine runs richer until warm. Another factor here in the States is that winter-blended fuels don't pack as many Btu's as summer blends.