Pour talcum powder over the dry erase marker stains on your car seat. Leave the powder on the upholstery for 15 minutes to absorb oily residue. Remove the powder with a handheld vacuum cleaner.
Pour 2 cups of water into a bucket. Add 1 tablespoon each of dishwashing detergent and white vinegar.
Wet a sponge with the detergent and vinegar solution. Squeeze the sponge to remove excess moisture.
Blot the marker stains until the upholstery is damp. Allow the solution to remain on the car seat while blotting the fabric every five minutes, with more solution, to lift the marker stains.
Remove the soap solution from the car seat by dabbing it with cool water. Press a dry cloth into the upholstery to absorb the liquid.
Moisten a clean cloth with rubbing alcohol. Dab at the remaining dry erase ink to remove it.
Treat any remaining dry erase marker stain with a solution made from 2 cups of warm water, 1 teaspoon of dishwashing detergent and 1 tablespoon of ammonia. Blot the car seat upholstery with the solution every five minutes, for half an hour.
Rinse the car seat by dabbing it with a damp cloth. Press dry cloths into the car seat upholstery to absorb moisture. Allow the surface to air-dry completely.