I had a long conversation about oils for engines and condensation issues re the Panda TwinAir. Long and short of it was he recommended sticking to the EXACT spec of oil and said engine tolerances are now so tight that manufacturers are designing engines around specific oils. I know one Acea C3 should be the same as another, but additives in brands may be more critical now than when tolerances were greater. I have always favoured the best possible oil particularly with turbo engines but have no evidence it makes any difference at all.
I had a company Astra 1.8 that had never had service since new 75K miles before. I ran this up to about 130K miles and it only ever complained after its first service at 75K. I had a Vectra with variable oil service intervals and the dealer told me they had never seen one before that did not require a change after 20K mine did in over 32K with no service indicator light showing. It did feel much better with new oil but was capable according to its self diagnostics of 40K between changes. It was of course drivenwith sympathy as if stolen 100% of the time doing 400-500 miles a day. I think we worry too much! - including me.