I've always used Mobil 1 in my A14Turbo, and i have never had a problem with it, but i did chnge the oil every 3 months when it was been driven on the road and it is still a relitively new engine, only about 2000 miles on the clock but it was driven hard.

A mate of mine who is a mechanic always uses Penzoil in his SR powered 1600 and he swears by it!

The only thing i can suggest is buy a good quaility oil, and in this case you get what you pay for can't be any more true.