if its asus, generally less than 1.65ish vcore in bios would be safe (as in reality it would be around 1.68-1.72 lol)
other than that, as stated above, look with mbm5 or wahtever program (if you get one with mobo, use that) to see what it is at
1.75v+ wont last more than a few months ive seen/heard
id stay under 1.65ish probably