It will be a crap shoot as to whether or not this device will help for a given model. For most modern vehicles, I'm willing to bet it would actually be detrimental. At least the very least, it may help for some conditions and hurt for others. Engineers put a lot of effort into optimizing charge motion these days. If there were such a device that could be put into the air stream that would improve fuel economy across the board, we'd be using it.