run in
phrasal verbPart ofrun
run in — phrasal verb
1. To use a new engine or machine gently for a period so it works well later.
1.片語動詞
釋義
To use a new engine or machine gently for a period so it works well later.
例句
You should run in a new car engine for the first 500 miles.
The mechanic said to run in the lawnmower slowly.