I did an spi to zetec engine swap. The engine runs fine there's no engine codes I had an emission test done, the readings were what i'd expect from a brand new engine which it basically is. (4500 km on it) Had an O2 sensor go so i changed it. Anyone have any ideas what it could be. My grandfather has the same car/ engine and gets 600 km to a tank. My car get's 400 km to a tank. I'm easier on my car than my grandfather. Anyone have any ideas.