Fast Running Time of C in C++ Judge

Would it be of significance if I write my C++ program entirely using C libraries and submit it using C++ compiler in online judge. It runs faster on my PC, but can it really save me from getting a TLE where my C++ program crosses over the limit. (although the algo remains same)

Time limit for intended solutions are not so tight. So, If it passes in one language then it will pass in other languages as well.