I went to the Porsche dealer in town here and the parts guy quoted me $48.00 a quart (964ml) for OEM Porsche MT Fluid. I almost swallowed my gum I gasped so hard.
The service manager happened to be there and he tells me the stuff is made by Royal Dutch Shell in Europe but it is the same stuff, 75W90 GL-5, available from Quaker State in North America, a subsidiary of Shell. He further tells me that although Porsche specified GL-4 when the Boxster first came out years ago, the GL-5 spec today meets all of Porsche's requirements. Something about the sulfur molecules are now compatible with sychros and high pressure differential gears. A little too technical for me but he said they issued a TSB a few years back now specing the new GL-5 formulations.
Anyway, long story short, I thanked the service guy at Porsche but told the parts guy I can't justify $150 on MT Fluid when Quaker State 75W90 GL-5 sells for about $18.00 a quart at most auto supply places and Crappy Tire sometimes has it for less.
So I picked up 3 quarts of Quaker State and I will be changing the fluid on Saturday. I have 74,000 Km (46,000 M) I am doing all fluids over the next few weeks but starting with engine oil and MT.
I'll let you know if I feel any difference in shifting. Currently it is a little 'notchy' when cold but is fine when warm.
