The introduction of the Renault Transmission on the Esprit to replace the Citroen Transaxle (Type C35) was a major exercise. The project started using the Renault specified Elf TRX lubricant. Following some durability testing it was found that this lubricant was not suitable for the Esprit application. Following discussions between Renault Engineering and Lotus it was decided to revise the lubrication to a specification that Renault were evaluating.

This product was produced by Mobil and was designated as Mobil 630M. The gearbox testing (including things like cold shift quality and operating temperature control) continued using Mobil 630M. The vehicle testing was to a programme that met both Renault & Lotus durability requirements using both test circuits (Nardo & Millbrook) and European Roads (Mainly Germany & Switzerland).Many Vehicles & Gearboxes were subjected to the durability cycle and complete Gearbox strip & inspection was carried out by both Renault & Lotus Engineers.

Only after the Renault identified durability had been completed was the Gearbox approval given provided that the Gearboxes were filled with Mobil 630M. At this time the Gearbox was identified as the Renault UN1-16. The Mobil lubricant was specified for a number of years until we were advised that it was being phased out and would eventually disappear from the market place. Some Mobil 630 lubricants still exist but unless it is identified as 630M it is different to that approved by Lotus.

During the life of the Esprit the vehicle specification was updated several times. This led to changes to the Transmission (to cope with the increased Engine Torque) developed by Renault for the Esprit application (High Torque known as UN1-026). During the development of the High Torque Transmission different lubricants were tested to ensure reliability with the increased vehicle performance. The most successful lubricant for all round performance and durability was found to be Castrol TAF - X. This lubricant was specified for all Lotus Esprit Renault Transmission applications

Many lubricants may offer benefits of some sort (shift quality, cold operation, noise etc.) but the Castrol has been extensively tested by Lotus and found to be our preferred lubricant. All the comments on the net about Lotus making the lubricant choice on things like cost, company connections etc. are incorrect. The lubricant specification was made on Technical Merit only. The Castrol TAF - X met all of our requirements for our increased engine performance (including the V 8).

The Gearbox identification is currently Renault UN1-027 for the Esprit V8 and Renault UN1-028 for the Esprit GT3. Castrol TAF - X is available from Lotus under the Part No. A082F6552S. This statement reinforces the words of Dave Simkin of Lotus Cars USA following an enquiry on lubrication specification.