Hi there. Renault use Elf Tranself 75W80 gearbox oil which is specifically for the six speed gearbox. As far as I know it is only available from a Renault dealer in 5 litre containers and I paid £18.50 last week. You will need to drain the gearbox while the oil is hot and refill it with exactly 2.2 litres. You will need a piece of PVC tubing and a funnel as the filler hole is very awkward to get at. I threaded the tubing down through the engine and then pushed it into the filler hole about 6 inches. Pour the oil in really slowly and get someone to check that you are not losing any out of the filler hole, otherwise you won't know for sure that you have put in the correct amount. Good luck!