Paul,
I put Castrol 5W50 in a recently rebuilt (8000km) 1.9 WB last summer and I have had no problem with leaks.
George    
"85 Westfalia

>>The numbers show synthetic does a great job of >>cooling the engine.  I don't
>>like the conclusion statement though:  "Of course, the >>car now leaks because
>>of the viscosity of the synthetic oil, but I guess we >>halfway expected that."