well, a problem arises with oil/fat substitutions -- you can't just swap veg.oil (usually hydrogenated soybean/corn/cottonseed oil) for equal amounts of butter. there's the liquid/solid factor and the heat-tolerance. theoretically you could use peanut or olive oil instead of veg.oil, but sometimes you're dealing with something that won't taste right with either of those.

have you tried coconut oil? it has a lower melting point than solid veg.oil (crisco), but better heat-tolerance (higher smoke-point) than butter.