I think that would be fine. Of course, some things shouldn't be sprayed. All in all, if you wash the car enough in the winter and really spray all up underneath the car to get all the salt off, you'll do okay as well. I'd imagine the newer STIs have an underbody coating but I'm not sure....a large amount of the underbody of my 04 is coated. For moving parts, joints, etc. you can coat with a heavy spray on grease, if you can find it. This is all optional of course.