Jouk
There was an article on top gear or something like that a couple of months ago and it was said that all them gadgets are pooh,
If they were that good the oil companies and car mfrs would be fitting them as standard.
I can remember the magnatheripy bracelet companies trying to con pensioners into thinking they were a cure for everything, even down to putting one on your water supply at home , then there was one for your car an even more expensive one if you wanted to save more fuel , they even sell them for your pets.
You buy one and i guarantee you will be chucking your money away