The Jaguar XJ is the name of a series of full-size luxury cars sold by the British automobile brand, Jaguar Cars since 1968. Since 1970 they have been Jaguar's flagship. The original model was the last Jaguar saloon to have had the input of Sir William Lyons, the company's founder, and the model has been featured in countless media and high-profile appearances. The current Jaguar XJ was launched in 2009. It is one of the cars used by the British royal family and an armoured version is used for transporting the UK Prime Minister. he XJ6, using 2.8-litre (2,792 cc or 170.4 cu in) and 4.2-litre (4,235 cc or 258.4 cu in) straight-six cylinder versions of Jaguar's renowned XK engine, replaced most of Jaguar's saloons – which, in the 1960s, had expanded to four separate ranges. Apart from the engines, other main assemblies carried over from previous models were the widest version of Jaguar's IRS unit from the Mark X and the subframe mounted independent front suspension first seen in the 1955 2.4-litre with new anti-dive geometry. he car was introduced in September 1968. Power-assisted steering and leather upholstery were standard on the 2.8 L De Luxe and 4.2 L models and air conditioning was offered as an optional extra on the 4.2 L. Daimler versions were launched in October 1969, in a series of television advertisements featuring Sir William. In these spots, he referred to the car as "the finest Jaguar ever". An unusual feature, inherited from the Mark X and S-Type saloons, was the provision of twin fuel tanks, positioned on each side of the boot / trunk, and filled using two separately lockable filler caps: one on the top of each wing above the rear wheel arches. Preliminary reviews of the car were favourable, noting the effective brakes and good ride quality.
In March 1970 it was announced that the Borg-Warner Model 8 automatic transmission, which the XJ6 had featured since 1968, would be replaced on the 4.2-litre-engined XJ6 with a Borg-Warner Model 12 unit