To sign oil, hold your flat, open non-dominant hand in front of you, lying on its pinkie side and with palm facing in. Then take your open, dominant hand, and grasp the underside of the non-dominant hand with your middle finger and thumb. Next, drag your thumb and middle finger downward as they touch, a few inches below the non-dominant hand. It is as if you are mimicking the fat or oil dripping from a piece of roasted meat, pork, or chicken on a skewer.
Teach your toddler the oil sign when they ask about this ingredient in the kitchen, as you are preparing salads and other meals using oil. You can also teach the other kind of 'oil' in relation to cars, trains, or mechanical devices needing some lubrication.
This is a useful flash card taught best in conjunction with cooking, transport, or machine flash cards.