Porsche first went 0W40 synthetic on the 993. I don't believe they changed any bearing clearances from previous models. The bottom end is basically the same since, right up to the GT3 models. They've stuck with 0W40 when everyone else went to 5W30. What they have changed is PCV systems, cam actuators,lifters, dry sump suction pumps. There's alot of extra machinery to lube in those engines compared to an L4 engine plus all of it it laying over sideways. Other considerations are oil intervals, emissions and preventing leaks. The GT3 has higher crankcase vacuum also. The mainseal will leak if it's not running.
I agree that running the optimum weight oil can reduce temp and increase HP. It doesn't necessarily help using synthetic. It takes more effort to pump 50WT than 30WT, which produces heat.
When i switched to 0W40 synth.(VW 1.8) from 10w40 regular, I noticed no diff in press or temp. However the valve train sounded like it was going to come apart. I surmised that solid lifter/cam clearances and lifter/head were too loose for synthetic. Plus synthetic still gets just as dirty, just as fast from blowby and condensation. Porsche has taken great lenghts with their PCV systems using cyclone separators, check valves, computer controlled valves even changing hose dia., all to manage oil mist separation and condensaion in the oil. Not to mention the cost/qt. of synth. Much more cost effective to use regular oil if possible.
Dick Gagliardi
LoopRacing Scirocco II
H prod, Chicago Region SCCA
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