Unfortunately food was spilled in my passenger seat. Initially I cleaned it with warm water and a towel.
Now that it's dried, there are stains from the chicken grease.
What products should I use to clean the seats without damaging the material?
Many of the hot water carpet cleaners like rug Doctor will do well at cleaning it up. I would prefer treat the surface with a fabric cleaner and scrub it with a brush. Then come behind it with the rug Doctor filled with only water and wet the area and then diligently vacuum the water from the seat.
Try woolite and a soft bristle brush. if that doesn't work, try "SPOT SHOT" (test it in an inconspicuous spot first.. ive never had any discoloration issues from it, but you never know), and if that doesn't work, try wolfgang spot eliminator, it's pricy but it always gets the job done.
I have an old spray can of scotchbrite carpet cleaner I think, that foams up when you spray it on carpet/fabric. You let it set for a minute then wipe up with water. It is made for this and does an excellent job.
if its just grease you just need to get some soap in there then suck it out, possibly multiple times, if you have a good strong shop vac you can prob figure something out. just get some fabric cleaner, spray it on, use a soft brush and gently swirl it around. then use a shop vac to suck it up, make sure you clean the hose very well first. and dont brush it hard or un evenly, its very easy to leave a different kind of spot in your wake doing this.