V-power (I assume you're not from the UK then) is actually in some areas better than the Optimax that we get here, for example in Australia, technically it's a much better fuel.
Does the Marea have a knock sensor? If not, the only benefit of using optimax over a standard fuel is the cleaning ability of the fuel (This is the opinion of the chief tester at the Stanlow Oil Refinery's technology centre who I spoke to for some time about it). In his words, without a knock sensor, he wouldn't use it. The engine can't change it's ignition timing to take advantage of the higher octane fuel etc.