Transmission Oil?

I know there has been great discussion over the years regarding what transmission oil to use in our beloved X1/9's.

I have always replaced the oil with 'Redline MT90' as a lot of the 'XWEB Forum' people seem to use it. I've had no problems with this oil however I'm currently rebuilding my box and wondered if anyone can advise on a cheaper alternative as 'Redline' is over £70 to buy? I don't mind spending the money however there are cheaper oils at half the price.

Locally to me I can source the original 'ZC90' oil at around £40's.

Any advice greatly appreciated.

I think it is really down to your judgement of the value of going for a modern synthetic oil rather than what is now a pretty old formula mineral oil. Obviously the ZC90 will be OK in the car as this was the original spec. I don't know if there would be any obvious improvement in operation of the transmission but a more modern oil would probably last longer and maybe give better protection to your rebuilt box. For the sake of £30 quid or so, I would think this is probably worth it.

Ian, thanks for the reply. I decided to go for the 'Redline' oil as I have used this oil before and it is highly recommended by a gearbox specialist local to me. So thanks once again!