Since the discussion in the locked section does not really deserve to be locked I'm continuing my responces here.

The 75 mpg claim is with the optimistic Euro drive cycle likely wiht the new Ingenium 2.0L diesel engine. From Jaguar press releases:

The first Ingenium engine to go into volume production, a 2.0-litre diesel known as AJ200D, friction is reduced by 17 per cent compared to the current engine, helping to make it one of the most efficient and responsive 2.0-litre turbo diesels in its segment. Ingenium engines feature six key technologies that combine to reduce friction, add refinement and improve performance. They include:

• Roller bearings on cam and balancer shafts, instead of machined-in bearing surfaces.
• Computer-controlled variable oil pumps that save energy by delivering the optimum amount of oil at all speeds, engine loads and temperatures.
• Computer-controlled variable water pumps that adjust the amount of coolant flowing through the engine, based on temperature, speed and driving conditions. The split or twin circuit cooling system offers the twin benefits of lowering C02 emissions by enabling fast warm ups, and providing quick cabin heat on cold days.
• Simplified cam drive system designed for modular application.
• Crankshafts that are offset from the centre of the block.
• Electronically controlled piston cooling jets to improve efficiency in the oil pumping circuit. Jets are switched off when piston cooling is not needed. They also enable the engine to reach its optimum operating temperature faster, further helping to reduce C02 emissions.