How do I clean my very dirty fabric car seats?

Have you thought about the Carpet Rental machines? I bet they would work. Most Walmart has a rental place.

I used a damp microfiber cloth to get off surface dirt & a lot came off then rinse & use a spray cleaner on remaining stains. Rinse & let dry then vacuum. Worked great was surprised.

If the dirt is grease from foods, dampen a white cloth in warm water and spritz a good degreaser on cloth. If it's dust and general surface dirt, brush the seats first then just a dampened cloth with a low suds cleaner. White towels are good to show how clean the seats are and soak up any dampness more quickly.

If you want to do for free and happen to have a shop vac, vacuum first, then use a spray bottle just mixed with a little dish or laundry soap and spray the seats. Give it a few seconds to soak in and then vac it up. Reapply to any more stubborn stains. If you don't have a shop vac, you can use a car wash place or gas station that has vacuums available as well. Next idea is to go to an Auto Zone or Advance Auto or Pep Boys and they have products especially made to do this.that cost about 10.00.

See if these tips help . . .

https://www.best-auto-detailing-tips.com/how-to-clean-car-upholstery.html

https://m.wikihow.com/Clean-Car-Upholstery

My husband uses an upholstery cleaner.

I am looking for home-made upholstery cleaner.

https://www.finalrentals.com/monthly-car-rentals-dubai-abu-dhabi Make a vinegar solution. In a bucket, combine a cup of vinegar, a few drops of dish soap, and about a gallon of hot water. Then dab the mixture into the stain and scrub it out with a brush, then rinse the seat with clean water.