Can sunflower or coconut oil be substituted for vegetable shortening in cake icing? I was reading this recipe for cake icing and was wondering what would happen if I substituted sunflower oil or coconut oil (which is thicker and may better model the texture of the shortening) for vegetable shortening. I don't eat vegetable shortening/margarine/crisco and am looking for a way to adapt this recipe.

4 lb powdered sugar
1 TB cream of tartar
1 1/4 c. of white shortening (crisco ... the sticks are easy to measure)
a pinch of salt
1 TB extract of your choice
3/4 to 1c. of water (maybe more depending on humidity)



  Put all ingredients except the water into a mixer. Add 3/4 c. water,
  and slowly add more to make the consistancy of your choice. Mix on low
  speed 'til mixed, then on #6 or 8 for 6 to 7 minutes. Consistency
  should be "creamy" -- like cream cheese when soft. Stiff icing should
  be creamy also.
I don't know for sure, as I've never tried, but I doubt it would whip up into the right texture. Shortening is already a solid, so you're just introducing air. Sunflower oil is a liquid, so you'd want to solidify it somehow to make frosting.