It is a 1.6T with direct injection requiring 98. No idea, but over a few years it always gets consistently and measurably better fuel economy with BP. I have had other cars over the years that seemed to have a preference for one or other brand, and some that had no preference.
The only possibility would be the additive package (specific mix of detergents, etc) since it all starts from the same tanks in the same terminals. The vendor specific additive mix is put in when the tankers are being filled.
