Setting the voltage to auto is generally not a good idea, the mobo usually compensates far more than required for an overclock, that is why it is better to set a voltage and work your way up.
I recommend 1.25v as a starting point and then increasing the multiplier until you reach unstability at which point increasing the vcore will help. Obviously keep an eye on the temps but I would say upto 80/85c in stress testing is fine because in general everyday usage or gaming the cpu won't ever reach those temps.
I have posted a few guides and one of mine own in the Sandy Stable club. In the OP you can find links to various threads where you can find all the help required to overclocking your chip, better yet check out my guide
The spreadsheet in the OP of the Stable club consist's of user's posting their stable clocks with temperature readings and voltages after running stability testing. If you scroll to the top of the spreadsheet you can select different sheets that enable you to make comparisons while you do your own overclocking. Link to the club is in my sig
Hope that helps.