I have worked in the car industry for over ten years, everything from development of novel fuel-efficient engines to mapping of production vehicles. In that time I've seen dozens if not hundreds of supposed "fuel saving devices" advertised. Without exception, I advise you not to buy them! On this page I'll explain why you should be sceptical about add-on fuel "saving" products. (More: http://www.fuelsaving.info/debunk.htm )
Recently due to rocket high Petrol price stituation many people are looking for an alternative way to save petrol cost. Some may have decided to try some of those so-called Fuel "Saving" gadgets now. My advice to you all please think twice before buying those products, you might end up with no Cost Saving but extra expenses, in worst case your Engine might be damaged. Good Luck!