If you are faced with a musty-smelling car, moisture is likely the cause. Whether your car windows were left opened in a rainstorm, or you spilt water on the car upholstery or carpet, moisture in the car interior will cause mildew to form. Mildew will then leave a musty odour in the car. You can remove musty odour from your car by giving the inside a good cleaning. You probably have everything you need at home to deodorise a smelly car interior.
Soak up any visible puddles of moisture. If you have access to a handheld vac, use it to extract water from the interior of the car. If not, use rags to firmly blot any visible moisture from the car. Turn on the car and set the heater to high. Allow the car to run idle for a couple of hours to dry out any wet spots.
Scrub any visible mildew from the car interior with a dry scrub brush. Follow up by vacuuming the interior to further remove the loose mildew.
Fill a bucket half full with warm water. Add a few squirts of washing up liquid to the water. Use your hands to lather up the soap and water to create soap suds.
Scoop the soap suds only from the bucket using a rag. Scrub any mildewed areas of the car upholstery or carpet with the rag and soap suds. Go over the areas with a slightly damp rag to remove the soap residue. Avoid using too much water when cleaning or you will be faced with further mildew growth.
Sprinkle a generous coating of baking soda onto the car upholstery and fabric. Sprinkle the baking soda throughout the entire vehicle, not just mildewed areas.
Let the baking soda sit on the interior of the car for at least 15 minutes. Use a vacuum cleaner to pick up the powder.
Fill a small bowl with white vinegar. Place the bowl on the floor of your car. Let it sit overnight in the car to further absorb the odour.
Keep the windows down (as long as it is not raining) and park your car in a sunny spot to help dry up any moisture. If your car interior is leather, wipe down any mildewed areas of the upholstery with a mixture of 237 ml (1 cup) denatured alcohol and 237 ml (1 cup) water. Place a few cotton balls soaked with pure vanilla under the seats of the car. This will help to freshen up the car. Unused dryer sheets will have the same effect.