May be worth checking... Super unleaded was pretty much taken out of the british fuel market. You need a special catalytic converter for it, to remove the harmful emissions (not the same as for regular unleaded).
You can use regular in something designed for super, but not the other way around. Of course it could just be that what you call super, isn't the same as what we did.
But it was a fact, never widely know in Britain, lots of people were filling up with super when they shouldn't. (also it was removed here because it was found to be a lot more carcenagenic than regular)
just my 2 pence