Here's a review from Amazon that says it works for this exact purpose...
Amazon Verified Purchase
This product is not only wonderful for static cling associated with clothing, but it works great for static cling and shocks associated with fabric car/auto upholstery and car/auto carpeting. I use it regularly for this purpose. When I first got my new car I noticed that every time I got out and shut the door I would get a static shock caused by a static charge build up from the fabric used for the car's upholstery. I purchased a can of Static Guard Static Cling Spray here on Amazon and sprayed the car's upholstery and carpeting and it has completely resolved this issue. I reapply it once a month.
Heh. DJ2014 and I posting at the same time.