What happens if I use vegetable oil instead of machine oil or grease?
Oil of any kind is the wrong lube to use on hinges.  Oil, WD40, or any petro based product wets the hinge surfaces and will collect dust and dirt.  I always recommend dry silicone spray. Silicone works great, won't harm surrounding finishes etc.  Some folks like graphite, but I find it a bit messy to use.