This video shows you how to remove a stain using a homemade carpet cleaner using vinegar and clothes detergent. The video shows you the process of removing the stain from the carpet, but it doesn't really you show how to mix a homemade carpet cleaner. The ingredients are fair but I would replace the clothing detergent with a mild dish soap. Clothing detergents are designed for full immersion cleaning in a machine that cycles the cleaning process. They really do have too much soap in them and can leave a residue that can attract more soil after cleaning the spot. Dish soaps are have a more mild soap that can be rinsed away easier.
As a professional carpet cleaner in Tampa FL I deal with a lot of tough carpet stains on a daily basis and I use professional strength cleaning solutions on the job. I have also used a lot of in home solutions to get the job done when necessary. There are a few go to ingredients that I use in a home made carpet cleaner. The base of my cleaning solutions is always 2 cups of carbonated water. The bubbling action helps break up soils and lifts them to the surface to be removed. I use 1/2 teaspoon of vinegar to reduce the pH of the cleaning solution and help kill bacteria will cleaning. Then I add a few drops of dish washing detergent. I don't use more then 5 to 7 drops in the cleaning solution it seams to do the trick for breaking up oily substances.
This mixture can be sprayed on with a spray bottle or poured on right our of the measuring cup. You can follow the video above for application purposes. Just remember to blot the spot and don't scrub. Scrubbing will help set the stain in and could damage your carpet. If you can't remove the spot with this homemade carpet cleaner it's probably time to bring in a professional carpet cleaner.