Though only produced for three years, the Jaguar X300 has since become one of the most respected cars in the company’s history; its predecessor, the XJ40, though technically advanced, had never aroused the same emotions as previous three generations of the XJ saloon. In addition, the XJS had been in production for nearly 20 years, and its replacement the XK8 was still two years away. What the company therefore desperately needed was a car that would appeal to both the traditional Jaguar buyer, many of whom had been alienated by the XJ40, while still appealing to the younger, more sporting BMW and Mercedes driver. The X300 did all this and more, achieving that rare feat of a facelift proving more cohesive and elegant than the original design.

With good proportions, proven underpinnings and a near bulletproof engines, the basic idea was stunningly simple; re-skin the XJ40 in the style similar to that of the Series 3 XJ6, refine the powertrain even further and, for the younger market, provide a sporting variant with real performance. In practice a huge amount of work was needed to get the detailing right and ensure that the new car developed an identity and character of its own rather than becoming a mere caricature of the past, an accusation that has dogged the new Volkswagen Beetle for instance.

So, below those curvaceous new lines lay a largely unmodified late XJ40 body structure, the biggest changes being at the front and rear to accept the new lamp housings. One small but important difference is the smooth transition from the rear pillar to the top of the rear wing, instead of the awkward plastic trim piece needed on the XJ40 – a clear example of the advances in manufacturing processes between 1986 and 1994. Other new features were the use of colour matched oval door handles in place of the earlier square edged chrome type and curved integrated bumpers with stainless steel inserts. The door mirrors too are more flowing, with painted or chrome covers according to model, while the leak prone recess between the rear lamps for the number plates was replaced with a shallow depression in the boot lid and a much simpler plinth. The roof, door structures, floorpan, sills and glass, all expensive to redesign remain essentially unchanged from the XJ40.

The well respected 3.2 and 4.0 AJ6 engines were developed even further and re-named AJ16; the almost completely redesigned head featuring a stiffer casting, thinner, lighter valves, new camshafts and a lightweight magnesium cam cover that housed a separate ignition coil for each cylinder, the distributor being replaced by a TDC sensor. Together with changes to the bottom end resulted in a noticeable improvement to refinement along with a healthy rise in power and torque.

The big news however was the supercharged 4.0-litre engine fitted to the XJR, now a mainstream model and with the emphasis firmly on performance rather than classic luxury, the XJR boasted enough performance to eclipse even the mighty V12. Featuring the same Eaton blower as the 3.2 litre Aston DB7, the 4.0 litre XJR was tuned more for low down torque than outright power but its 6.6 second 0-60 acceleration time was still only one tenth of a second behind the hand built XJR-S of only a few years before.

The V12 cars did continue though for those customers who preferred near silent acceleration to the turbine like whine of a supercharger and could afford the increased running costs. The engine itself remained largely unchanged except for a switch from distributor ignition to coil packs. 

Underneath, the suspension layout remained basically unchanged, new cast iron rear wishbones having been introduced on the last XJ40s. Self levelling rear suspension was no longer available even as an option, but there were new bespoke Bilstein dampers for the sporting models. Brakes reverted to vacuum boosting for the first time (on a saloon) since the Series 3 XJ, and while the calipers remained ATE, the rear discs became ventilated with larger discs fitted to the front of V12 and supercharged cars. A new traction control system, fitted to the XJR and V12 cars used the ABS system to brake a slipping wheel while an electric motor simultaneously pulled back on the accelerator cable to reduce throttle. 

Even when it came to the interior a good deal of late XJ40 structure remained, with similar seats, only slightly modified door trims and standardisation of the Daimler dash casing with its deeper wood panelling. The centre console was however completely redesigned to house the digital controls for the new Nippondenso climate control system, while, for trip computer operation, the keypad alongside the steering wheel disappeared in favour of a much simpler push button on the end of the indicator stalk. The X300 was also the first Jaguar saloon to include an industry standard OBD2 diagnostic connector beneath the dashboard, a full six years before they became mandatory.

While in its later years a stretched XJ40 had become available to special order, for the X300 the longer wheelbase became a regular option, with the cars built on the main production line and available with every engine except the supercharged 4.0 litre, with many 3.2 litre LWBs built for the chauffeur trade.