That is a safe proposition, but in a way you'll be 'wasting' the PS4S' capacity in the rear untill you change the next set.
Personally, I would sell these two perfectly fine Pirellis and get four 4S'.
My reasoning is that we only have this car a limited time and it's a bit of a shame to save those last few quid on a car costing many thousands to optimise economy instead of driving. Otherwise might as well gotten the base diesel version... And even there, I would always get the best tyre, from an energy perspective perhaps
Personally, I would sell these two perfectly fine Pirellis and get four 4S'.
My reasoning is that we only have this car a limited time and it's a bit of a shame to save those last few quid on a car costing many thousands to optimise economy instead of driving. Otherwise might as well gotten the base diesel version... And even there, I would always get the best tyre, from an energy perspective perhaps