I infuse a lot of herbs for soaps and salves/balms. I can't say that I have ever noticed that one oil is better than any other. I prefer liquid oils, if you use a solid fat you would have to infused with heat to keep the fat/butter liquid. I usually infuse at room temperature over 6 weeks, but I have done quick infusions with a water bath and low heat. I use olive, almond, avocado or sunflower oil depending on what oil I want to use for what application.