2.8VR6, which oil?

[S3 rich]

not really done any research, but someone told me semi-synthetic but not sure of grade?

is it not possible to use fully synthetic?



also, after a good run my engine starts to sound a bit unhappy, as if the oil its running is degrading when hot? when fully cooled down (ie oil thickened up) it sounds fine again smooth & no noise

could this be because it may have the incorrect oil in??

any help appreciated

Richard