(I) wouldn't (do something) if I were you

(I) wouldn't (do something) if I were you

A suggestion or warning that one not do something. "Do something" is sometimes omitted if the action in question is stated by the other person. I wouldn't speak to the boss like that if I were you, or you might end up getting your hours reduced. A: "I was thinking of quitting my job and getting into acting—what do you think?" B: "I wouldn't if I were you, to be honest." A: "What happens if I pull this lever?" B: "Wouldn't do that if I were you—that controls the airlock!"
See also: if
Farlex Dictionary of Idioms.

(I) wouldn't if I were you.

Fig. a polite way to advise someone not to do something. Mary: Do you think I should trade this car in on a new one? Sally: I wouldn't if I were you. Bob: I'm going to plant nothing but corn this year. Sue: I wouldn't if I were you. Bob: Why? Sue: It's better to diversify.
See also: if
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • a fast talker
  • all righty
  • a walking
  • a walking (something)
  • a/the feel of (something)
  • all right
  • a straw will show which way the wind blows
  • (one) could use (something)
  • a crack at (someone or something)
  • (one) doesn't give a rip (about something)