Can you substitute butter in a box cake recipe that calls for oil? Possible Duplicate:
  Conversion rule: how to switch oil and butter?  




Most box cake mixes call for adding oil and water. What would be the effect of using butter instead of oil, and what ratio should be used to substitute butter for the oil? 1:1?
I would do a 1:1 ratio with the following caveats - 

First make sure you are using unsalted butter (if you use salted it will change the flavor and the texture of the cake, usually not in a good way)

Second, I would clarify the butter (i.e. melt it skim off the foamy/cloudy bits that float at the top)

After that I would use an equal ratio. Be warned that the clarification process will reduce your butter a bit (8 tablespoons averages about 6 tablespoons after clarification), so make sure you measure after clarifying.