[4] The first generation Jaguar XJ was produced for a total period of 24 years, with two major facelifts – in 1973 and in 1979, with a raised front bumper and less tall grilles.

It carried over the 2.8-litre (2,792 cc (170.4 cu in)) and 4.2-litre (4,235 cc (258.4 cu in)) cylinder versions of Jaguar's renowned straight-six XK engine, and front and rear suspensions, from previous models: the widest version of Jaguar's IRS unit from the Mark X, and the subframe-mounted independent front suspension first seen in the 1955 Mark 1, with new anti-dive geometry.

Air conditioning was offered as an optional extra on the 4.2 L Daimler versions, which were launched in October 1969 in a series of television advertisements featuring Sir William.

An unusual feature inherited from the Mark X and S-Type saloons was the twin fuel tanks, positioned on each side of the boot, and filled using two separately lockable filler caps: one on the top of each wing above the rear wheel arches.

[8] The new transmission had three different forward positions accessed via the selector lever, which effectively enabled performance oriented drivers to hold lower ratios at higher revs to achieve better acceleration.

A high-performance version called the XJ12 was announced in July 1972, featuring a simplified grille treatment, and powered by a Jaguar's 5.3 L V12 engine coupled to the Borg-Warner Model 12 transmission.

[9] Bonnet louvres such as those fitted on the 12-cylinder E-Type were rejected and instead the XJ12 featured a complex "cross-flow" radiator divided into two separated horizontal sections supported with coolant feeder tanks at each end.

[13] By this time, the first customer deliveries of the two-door coupe, which retained the shorter standard-wheelbase (and which had already been formally launched more than a year earlier) were only months away.

[19] The economic troubles resulting from the 1973 oil crisis unfolding in the Western world at that time seemed to have reduced any sense of urgency about producing and selling the cars.

[citation needed] The delayed introduction, the labour-intensive work required by the modified saloon body, the higher price than the four-door car, and the early demise promulgated by the new XJ-S, all ensured a small production run.

[citation needed] The XJC was also raced, although the results were less than satisfying - memories of the failed effort made British Leyland decline to provide factory backing for the TWR-prepared XJS five years later.

With Derek Bell at the wheel, it briefly led its debut race, the RAC Tourist Trophy at Silverstone in September 1976, but failed to finish.

This became the modus operandi for the XJC racing effort: Overweight and unreliable, the best result was a second place at Nürburgring in 1977 and British Leyland cancelled the program before completing the season.

[19][22] Production count[23] The car was significantly facelifted again in April 1979, known as the Series III, incorporating a subtle exterior redesign by Pininfarina.

In 1981, the cylinder heads of the V12 engine were replaced by the new Fireball high-compression design by Swiss racing driver Michael May, and were badged from this time onwards to 1985 as "HE" (High Efficiency) models.

The project suffered a number of delays due to problems at parent company British Leyland and events such as the 1973 oil crisis.

With 25% fewer body panel pressings required versus the outgoing model, the new process also saved weight, increased the stiffness of the chassis, and reduced cabin noise.

The X300, introduced in October 1994 at the Paris Motor Show, was stylistically intended to evoke the image of the more curvaceous Series XJ models.

In a Car and Driver's comparison test, it was stated that the X300 Jaguar XJ is less roomy than the E39 BMW 5 Series and W210 Mercedes-Benz E-Class despite being longer dimensionally.

[31] The X308 kept much of the same exterior styling as its predecessor, carrying its rounded four-headlamp bonnet, low roofline, sloping tail, and wrap-around rear light clusters.

The new fascia also allowed for the restoration of a proper glove compartment, which had been lost when the original XJ40 dash had been retrofitted with a passenger side airbag.

[33] The major mechanical change was the replacement of both the inline-six and V12 engines with new eight-cylinder AJ-V8 in either a displacement of 3.2 L or 4.0 L, with the 4.0 L also available in supercharged form in the Jaguar XJR, a sport-oriented model.

An optional touch screen interface controlled default settings, satellite navigation, the Alpine audio system, and bluetooth telephone.

The front has clear links with the XF executive car, although with slimmer, sleeker lights and a larger, squarer grille add a more aggressive appearance.

The upright, swooping taillights, nicknamed "cat's claws", and black roof panels at each side of the rear screen, which aim to hide the XJ's width, are the most striking aspects.

[41] The X351 received a minor facelift in 2014, primarily upgrading the suspension and rear seat facilities on the long wheelbase versions, but also introducing small cosmetic changes across the range, and making stop-start technology standard on all engines.

[43][44] On 5 July 2019, Jaguar Land Rover confirmed that they intended to build an all-electric XJ luxury saloon car at their Castle Bromwich plant.

[48] On 15 February 2021, Jaguar Land Rover announced that the all-electric XJ project had been shelved, as it was no longer part of the company's current vision.

[49] The company said: "Following a thorough technology review against the exponential change in the automotive industry, we concluded that the planned XJ replacement does not fit with our vision for a reimaged Jaguar brand.

"[50] Just prior to World War II, Jaguar, known then as SS Cars, started using a numbering system beginning with the letter X for internal projects.