Look what Uncle Ferdie has made for his cars... http://www.porsche.com/uk/accessori...ineparts/producthighlightsandneweditions/oil/ Note his oil is 20/50 for flat fours
After mine has done 500-1000 miles on SAE 30 while running in, I will be straight back on to Castrol 20/50, which has served me very well for the first 38 years of my bus ownership. Tony