Remove the car mats from the car. If the tomato stains are on the mats, you can wash them outside the car.
Apply water to the tomato stain. You can either pour a small amount of water onto the stain, or dab at it with a wet rag.
Top the stain off with dishwasher detergent. The dish soap has ingredients in it that are extremely effective at removing the oil of the tomato stain.
Rub the dish soap into the tomato stain with a damp rag.
Rub an ice cube over the car rug stain. The extremely cold water of the ice will help pull up the tomato stain.
Dab at the tomato stain with a rag dipped in vinegar. The vinegar will remove the remainder of the tomato from your car rug.