You probably could... But I'd melt it first and let it cool. The only reason why oil and butter vary is the milk solids but I can't see it being a problem in a cake mix. I SUCK at cake mixes... ironic huh? I can do the best 10 step chocolate fudge wedding cake with ganache filling and white chocolate buttercream but you put a cake mix in front of me and I always stuff up the ingredients and there is usually only 2 or 3!!!! What the?!