depends on which university you are. also international undergraduates are not promptly hired by companies due to many obstacles. right now mechanical does most hiring, but it might not be the same when you graduate. Did you consider chemical instead of petroleum? regarding the pay scale it is among the  highest paid engg. majors. take your decision wisely. if your are a freshmen you can figure out in the next semester and can switch whichever you want.  being a chemical engg gives you many options to concentrate in one of many fields available(in you senior year or masters level). you can even switch to petroleum.
 i might be wrong suggesting you.