There are few things that you can try, but here is the best way I know how to get vegetable oil out of carpet. First blot as much as possible up with paper towels. Then add a layer of cornstarch and allow that to sit and absorb oil. Repeat this process a few times, put the cornstarch down, allow it to sit, vacuum it up. When it looks like you've made decent progress with this, then use a grease cutting dish soap such as Dawn. Apply a small bit of dish soap to a clean damp towel and scrub the area. Follow up with a carpet shampooer or steam cleaning.