The chocolate bar was delicious and gobbled up on the run and you didn't notice the stain on the seat until the next day, after it set overnight and re-softened in the morning sun. Now you have a mess that seems ingrained in the fabric of your car seats for all time. You can't sit on it without risking a stain on your trousers and you can't toss it in the washing machine, so how do you go about getting it out?
Let the chocolate reharden. Trying to scrub chocolate off the fabric when is it soft will only make it smear. To hasten the rehardening process put ice on the stain. Put the ice in a baggy and cover the baggy with a wash cloth. The baggy keeps the cloth from getting wet. Hold the ice gently on the chocolate stain until it hardens.
Scrape the chocolate with a butter knife. Be sure to use the blunt edge as the serrated edge could ruin your car upholstery.
Pick off and throw out the chocolate scraps.
Spray the stain with stain remover. Saturate the stain and let it sit for five to ten minutes so that the cleaner completely penetrates the stain.
Add cold water and scrub gently with the scrub brush. Blot the stain with water and a washcloth.
Make a paste by adding drops of water to a teaspoon of powder Tide. Keep adding water and mixing until you make a paste. Using your finger, rub the paste into the stain.
Put cold water into a cup and use the water and a washcloth to blot the Tide away from the stain. As you blot, the remainder of the chocolate should lift up with the paste. You will have to change the water in your cup a few times to make sure the Tide is completely off of the seat.
Lay paper towels down and run an iron, set on low, over the spot if any of the stain remains. This step is only necessary in the event chocolate traces are left after the above cleaning.
Use cold water as hot water just seems to set chocolate stains.