How to decide which gas saving products are good to opt for and how to add them

There are number of commercial gas saving products available in the market which are advertised as environment friendly devices that improve fuel efficiency. These product sellers claim that their product helps to increase the vehicle mileage which in turns saves your hard earned money. But whether the products offered by various companies really fulfil the promise or are they just the scams, this should be researched thoroughly before installing any device in vehicle. There are some good websites where pro and cons of different products can be compared.
While opting for any of the gas saving products, one should remember following points:
• Devices and additives have different performance on different cars and models. So, the result of additives shown in one car could not be achieved in other car.
• Before investing in any device, calculate the money required to buy the product and the expected saving. This would help to decide whether it will be fruitful to buy additives for your car or truck.
• To compare the difference of fuel efficiency, one should track the mileage for at least three full tanks before installing the gas saving products.
• Any improvement in the vehicle which is less then one mile per gallon is not significant.
• Do not have blind faith on sellers if they claim that EPA (Environmental Protection Agency) has evaluated the product. Ask for a copy of such report or cross check it on internet.
There are many gas saving products, gas and oil additives available that enhance fuel economy. Here is how to add additives in vehicle:
• Add gas additives to the tank of vehicle. It takes some portion of the tank and would reduce the volume of gas that one ultimately have.
• Additives could be magnesium, tin or platinum and are made to remove waste that deposit in the tank bottom over the time. 
• Fill the tank as per the requirement.
• Additives for oil are generally mixed with oil. It reduces friction and increase the oil velocity which result improved performance of the engine.
By using gas saving products and maintaining vehicle on regular basis, one can get better performance and can save good fraction of amount that is spend on high priced fuel.