[johnnydee]

I notice that you are in the UK so that might make a difference to what product are available and what your car was delivered with. There are a lot of issues about friction additives that are relevant to the oil that you choose. For instance, the Red Line tech people tell me that Porsches are originally delivered with trans oil with 3% friction additives. U.S. trans oils are formulated with 6% slip additives. Replacing the oil with 6% slip formula can actually create issues with the synchros having too much slip and therefore not slowing things down enough to go to the next gear when downshifting and creating wear on the dog teeth.

I have been running Red Line 75W-90 in street and race cars for over 15 years and have been very happy with it. The only proviso would be that if you do run it, mix the 75W-90 and the 75W-90NS (the NS stands for Non Slip) and has no friction additives at all. This will give you the desired 3% level. The regular 75W-90 has 6% friction additives.

Just FYI, for all the 901 gearbox folks out there, Red Line recommends to use ONLY 75W-90NS in those boxes because of the synchro design in those boxes. Before anybody hammers me about this on the forums, I am aware that for cars with limited slip differentials, there is a tendency for the diff to be noisier in lower speed/tighter corners with lower or no friction additives but this is not bad for the diff. Red Line sells a small bottle of friction additives that you can use to add (sparingly) to the trans until it quiets down to your satisfaction. For race cars, this is obviously not a issue. I would say that going above 3% would not be necessary or advisable based upon what I have learned.