To see if your oil is rancid, pour some of it on a spoon and smell it. If it gives off a sour odor, it is an indication that the oil has gone bad. Rancid oil will give off a stickiness. Thus, if your container is giving a tacky feeling in the interior of the spout, it’s time to throw it away. Other indications of the rancidity of your oil include a bitter taste, soapy texture, or a smell of chemicals. You can choose to take a small sip if you are unable to judge from the smell. A bitter and harsh taste is another indicator of rancidity. The smell of rancid oil is wide-ranging. If it smells anywhere close to a play-dough, nail polish remover, crayons, or old paint, you should be assured that the oil is unfit for use.