Dunno about dates, but I ran all my Escorts ('87 XR3i, '84 and '85 S1 RST's) on unleaded (except the '85, which apparently was "set up" for super unleaded, so ran it on that), all without any additives or LRP, and they all ran fine with no problems - well, apart from the XR3i, that blew up after it's first long journey, but that turned out to be a poorly looked after engine, and the long journey basically de-coked it and showed up how bad it was running. Or at least so I was told/led to believe. After I had that rebuilt, it ran sweet as a nut on regular unleaded, with no additives, for several years till I sold it.