Over time, vinyl will become hard and stiff if not properly cared for. Vinyl absorbs dirt and other contaminants that cause the surface of the vinyl to harden. Dried dirt, grease and body oil can cause vinyl to stiffen. The best way to soften the vinyl is to clean the surface of the vinyl with a specialized vinyl cleaner, then use mineral oil or an oil product sold specifically for use with vinyl to soften the vinyl and make it usable once more. This softening method will not help repair any cracks or scratches in the vinyl.
Soft bristle brush
Vinyl cleaning spray
Clear mineral oil
Wash the surface of the vinyl with hot water soapy water and a stiff bristle brush to remove the majority of the grease and dirt from the surface of the material. Rinse the vinyl with water and allow it to dry for two or three hours before moving on to the next step.
Spray the vinyl with vinyl cleaner and allow the cleaner to soak into the material for about five minutes. Wipe the material clean with soft cloths. Repeat the process until the cloth comes away clean.
Dip the brush in clean water and scrub the surface of the vinyl gently to remove stuck-on dirt and clean hard-to-reach areas. Allow the plastic to dry overnight.
Pour some mineral oil onto a soft, dry cloth. Rub the cloth into the surface of the plastic using circular motions. Rub each section for at least 30 seconds.
Allow the oil to sink into the vinyl for about one hour. Repeat the oiling process until the vinyl softens and becomes smooth and supple once more. Wipe away any excess oil with a clean, dry cloth.
Work with the vinyl on a warm day in a shaded area. This will prevent the material from drying out too quickly, which can damage the material or cause cracks to occur.
If you do not have mineral oil on hand, you can also use baby oil, or even cooking oil to soften the material. Leather conditioning cream can also be used to soften thick and stiff vinyl.
Allow the oil to soak into the vinyl over a period of several days for best results that will last several months or even years. Wipe up any excess oil before using the seat or other object to prevent clothes or other objects from getting ruined or stained by the oil.