I get a regular 370 on a tank full on long journeys and thats probably averaging around 90mph (obviously im in France and germany when doing this ), on short fourneys i get around 315-325 and I always use either Optimax 98 or tesco Momentum 99 (im sure someone will correct me and say that Optimax is 99 Ron, but it used to be 98 and I have seen no evidence of it being 99, hope to be stood corrected! )
Shell don't sell Optimax in this country anymore. They sell V-Power which is 99RON
I don't use anything but V-Power and Momentum-99 in my car. That's what VW recommend for the 2.0T. You can use a minimum grade of 95RON but that's not really meant to be regular. i doubt it does any harm tho.
i get much better fuel mileage from Momentum over standard petrol, and better mileage still with V-Power over Momentum. no explanation for that one but it's been consistently repeatable 3 - 4% improvement in mileage with V-Power over Momentum. now my car gets V-Power, or Momentum when there's no V-Power nearby and i'm really in need of a fill up.
i mean just to put things into perspective, V-Power is about 7p per litre more expensive at my local Shell. so that's about £4.20 more expensive on a full tank. but i get better fuel mileage, so that difference probably more around the £2.50 mark and the car runs better. £2.50 per 300 - 350mi is neither here nor there tbh.