Fuel consumption suddenly dropped?

Last year my Jaguar X-Type diesel's fuel consumption suddenly dropped from 52 to 44mpg.

I have put two lots of injector cleaner in the tank; changed the fuel & air filters; checked the MAF and DPF operations and the car still shows no faults on a diagnostic check.

Is there a common cause for this sudden change? My local garage say it is cheaper for me to continue to use it than it would be to diagnose and repair a problem!

I use the car for short local trips and also 250 mile motorway journeys.

Asked on 4 April 2013 by Daimler_SP250

Answered by Honest John
Various people offer stuff that is supposed to sort out the DPF. It might be that the DPF is not functioning properly and that the ECU is injecting excess fuel into the engine to try to clear it. Check the sump level. If that has risen, then this is is what is happening to the fuel.
Similar questions
My Kia Sportage MHEV seems to be doing 15% less mpg since the weather turned colder, with the battery power cutting in less regularly despite saying it’s well charged. Is this a fault with my car or something...
Why do summer and winter mpg figures vary?
I have a Jaguar XE, nearly two years old, which averages around 39mpg on the computer set for long periods. 2000 miles ago I decided to check real mpg by checking fill-ups against mileage and was surprised...
Related models
Smart looks and roomy load bay. V6s are four-wheel drive. Diesels are quite frugal.