Breaking in a new Yaris

[hystria]

engine: very small roughness on metal surface, will whip off in the first 1-2 hundred miles

oxygen sensor (sets the fuel/air mixture, therefore affects acceleration and fuel consumption): when new, it needs to get "burned" in order to operate to the specs. The hotter it gets, the faster it burns. I'd suggest, passing the first hundred miles, start shifting/keeping the revs higher than usually (above 4000rpm) and drive so 2-3 gas tanks.

don't switch to synthetics before 1000 miles, a new engine needs to run on mineral oil