Hi
If your worried and miles per gallon, maybe a Jaguar is the wrong car for you
Jaguar are Grace, Pace and Space, Its all about smiles per gallon, not miles per gallon
I think its Jaguars biggest downfall, Moving to Diesels, I bet they regret it now.
Though 28 mpg is really poor, I get 35.6 on a run in my S-type R, 4.2 petrol supercharged, Though I would;nt change it if it only did 20mpg
Cheers
Joe