Peanuts and peanut oil have the additional doubts attached to the species. If peanuts are considered to be kitniyos, then the peanut oil would present less of a problem then other kitniyos oils. Nevertheless, most reputable kashrus agencies in the United State and Israel do not permit the use of Shemen Kitniyos in their products. However, over the years, products bearing a Kosher for Passover certification have used kitniyos derived products. For example, one of the most prevalently converted products is corn syrup.
Corn syrup is one of the leading versatile sweeteners in the food industry today.
Corn syrup is made through the a conversion process, where the white starchy meat of the corn kernel is converted into sugar using hydrochloric acid and enzymes or less prevalently acid alone without the use of enzymes. The enzymes used are commonly derived from chometz, and in the corn sweetener industry today, enzymes are a key component in the conversion process. Since the final product is in liquid form, it was, and still is, considered to be Shemen Kitniyos by some authorities. Other Poskim posit that there is an intrinsic difference between classical Shemen Kitniyos, i.e. oil that is pressed out of the kernel, and a liquid converted from the actual kernel. The liquid is not Shemen Kitniyos, it is actual kitniyos.