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My car is a 1992 example with 48,000 genuine miles. I've always wondered if the gearbox oil was changed as I have no record that it has anything else other than the original factory fill. My thinking is that 24 year old gearbox oil may need a change! I'd purchased 2 litres of Castrol Syntrans Transaxle 75W-90 but had been putting off the oil change as I'd red on here was a sod it is to refill the box, well that's an understatement! Lotus really didn't have a strong design for service ethic did they!! Anyway, thanks to everyone whose already posted on here with useful comments, correct tools and removing the coolant header tank are essential. Jack the car up on axle stands so you can safely get underneath, I just jacked up the left side and put the axle stand under the alternative jacking point beneath the bolts securing the rear end of the front suspension rafts to the chassis front cross member (consult WikiLEC) if you're unsure. I also took advise from a member years ago and bought some rubber hockey pucks which I sandwich between the car and the trolley jack and the car and the axle stand for a bit of extra protection to the chassis. Once the header tank is removed you just about have access to the bolt retaining the speedo cable clamp (see picture to see how I did this with all my socket spacers), loosen it slightly and it will rotate clockwise to allow the speedo cable and gear to be withdrawn from the gearbox housing by about 30mm, just enough space to get a hose in to fill up the oil. Now you've confirmed that you can actually get into the gearbox to fill up, you can complete the relatively simple task of removing the gearbox sump plug and draining the oil. The plug is a great big thing on the bottom left side of the gearbox. It has a rubber O ring which squeezes into a chamfer counterbore, worth remembering when you re-tighten. Mine took a fair old force with a long ring spanner to remove, confirming it's never been removed before. To my surprize, 1.8litres of oil ran out into my collection tray (the old kitchen washing up bowl) and on closer inspection, didn't look in bad condition. I didn't test for additives but there was no debris that came out. Once all the old oil is out secure the sump plug and remember the rubber O ring has to be squeezed until you get a metal to metal joint, I couldn't find the specified torque. Now re-fill the gearbox with 1.8 litres of oil (see picture to see how I did this with garden hose and a funnel. Be sure the end of the hose is actually in the gearbox, its worth testing with a small quantity of oil first to make sure it is, you don't want 1.8 litres on your garage floor! In my case I was glad I checked as the end of the hose had indeed come out and so I had to juggle it back inside the gearbox past the speedo cable and gear. Once filled with 1.8 litres, the job is nearly done, remove the filling hose, jiggle the speedo cable and gear back into its home position, rotate the securing clamp back and tight the bolt securing the clamp, again sorry I didn't find the specified torque. Re-fit the coolant header tank and refill coolant. Remove car from axle stand. Job done!