Buyers GuideIn 1983 the then Toyota chairman Eiji Toyoda started a project called the F1 "Flagship No. 1 vehicle” also known as the "Circle-F" project, it was to produce a world-class luxury sedan for the international market.
The F1 project was not given a time scale for completion nor did it appear to have any budget constraints, as a result the vehicle was entirely new it did not use parts from the existing Toyota parts bin. The final cost of the development was more than 1 Billion US$
The car was designed to compete with and better all of the prestige models offered by the worlds existing manufacturers in all areas including aerodynamics performance and refinement.
As part of the development process 450 vehicle prototypes and 900 engine prototypes were constructed and they logged approximately 2.7 million kilometers testing in all climates and environments from winter roadways, to deserts in Arizona, Australia, the USA and Saudi Arabia.
In 1985 the first exterior models were presented to the Toyota management, featuring a low sports car type design, but by 1986 this had been changed to a classic three box design with a more upright stance, prominent grille, and two-tone paintwork
Wind tunnel tests were under taken and refinements made to the design to produce a very low drag coefficient for production vehicles of the time Cd 0.29.
In 1986, the Lexus marque was created to convey the launch of the flagship sedan and the vehicle was thenceforth known as the Lexus LS400. The design was finalised in 1987 with the chassis code UCF10.
Series 1 or MK I - 1989 (UCF10)
In January 1989, the LS 400 made its US debut. Sales began in September 1989 and exports to Australia, Canada, and the UK followed. The car was sold in Japan under the name Toyota Celsior. The car sold in North America for US$35,000 significantly undercutting the competition.
The LS 400's had an all new 4.0 liter V8 engine (1UZ-FE) and an all new four-speed automatic transmission. 
The chassis had an independent, double-wishbone suspension with an optional air suspension system. The car boasted a quieter cabin than virtually any of its competitors and the top speed of 160mph (250kmph) with a 0-60mph of 8.3 seconds beating all of the major competition offered by BMW and Mercedes-Benz etc.
The list of ground breaking features offered in the car is long. LS 400 was one of the first cars to feature an automatic motor driven tilt-and telescope steering wheel. It had SRS airbags, power adjustable shoulder seat belts, and an electro chromic rear-view mirror. The LS400 seated 5 people in comfort with trim in California walnut with leather power-adjustable seats. The dashboard featured an electroluminescent gauge cluster with visual effects.
Options included a Nakamichi premium sound system, an integrated mobile phone, gold badging and air suspension.
Series 1a or MK II - 1992 (UCF10 II)
A face lift model was issued in September 1992, it presented more than 50 changes to the previous car, these were in the main to respond to customer requests. The changes included a revised grille, additional body moldings, a larger selection of colors, an external temperature gauge, larger brakes and larger wheels and tires, the suspension and steering system were tweaked to improve handling.
Passenger safety was improved with driver and passenger air bags in the front and seat belt pre-tensioners. Chlorofluorocarbon-free refrigerant was added to the air-conditioning system.
Series 2 or Mk III - 1994 (UCF20)
The Second Generation Lexus LS400 was released in North America in late 1994 it had similar specifications to the previous model but it had been largely redesigned with a longer wheelbase to offer more passenger space and an upgraded 4.0 liter V8 engine (1UZ-FE) which now produced 260 bhp and 270 Ib ft of torque with and an improved 0-60 time of 7.4 seconds and better fuel economy
Improvements included more sound insulation, suspension updates, improved brakes,
a strengthened structure and the car had been lightened by 210 lb. Enlarged crumple zones, three point seatbelts to all seats and newly designed collapsible steering column.
Dual-zone climate air con controls were included and cup holders in the back, A new seat suspension system which used lightweight internal coil springs and stabilizer bars was included and an optional in-dash (glove box) CD changer was also offered.
The body had been subtly redesigned to be more aerodynamic (Cd 0.28) whilst retaining the general profile and contours of the original car. The new design featured sharper angles, curved body lines, and a beveled grille. With improved forward visibility.
The base model now cost US$51,000.
Series 2a or Mk IV - 1997 (UCF20 II)
A face lift of the UCF20 was issued in mid 1997 as the LS 400 (UCF20 II)
Revisions included a five-speed automatic transmission, increased engine output to 290 hp with a variable valve timing system. both the acceleration and fuel economy were improved by these changes
Again the suspension and steering were adjusted to improve handling and feedback. Styling changes included a new front fascia, side mirrors, and wheels a rear windscreen antenna replaced the conventional power ariel.
Passenger accommodation upgrades included a new trip computer, adjustable rear headrests, reading lamps, and-tinted glass, a micron filtration system was added to the air-conditioning system.
A CD based Satnav was added as an option (standard in the UK) a hard disk drive-based GPS navigation system was also an option in North America.
Additional safety features included front and side airbags and a vehicle stability control. The headlights were also equipped with a programmable delay feature for proximity illumination.
There is some cross over in the dates due to dealers running out old stock and the new models were not immediately available in all countries.
Series 3
The series three LS was issued in 2000 for 2001 it was in effect a completely new car having a new shape and larger engine and was known as the LS430 signaling the end of the LS400 model, it is not covered by this website.