If you have read my other pages on fuel "saving" devices, you will know that I am deeply sceptical of products claiming to work by methods unsupported by "conventional" scientific and engineering knowledge. Many people say, "ah, well, look at all the marvellous ideas that have come from maverick scientists in the past. Just because it's unconventional doesn't mean it's wrong". Typically people cite plate tectonics and Prions (as a cause of BSE) as examples of this.

To understand why this is false, it is necessary to understand what might be termed the "Scientific Method". This is, very roughly, how science and technology advances.

First, somebody makes a hypothesis (or "guess", as the legendary Richard Feynmann put it). This is an idea about how the world works, possibly based on some simple experiments, or possibly purely conjecture. Examples of such hypotheses would be "the Sun is at the centre of the solar system", "Prions cause BSE", or "putting a magnet round the fuel line improves economy".

The idea is then considered by the scientific community and, crucially, a way of testing it is devised. Any useful hypothesis must make testable predictions; that is to say, you can devise an experiment, where one result would mean the hypothesis is false, another result would mean it is true. Depending on how radical the idea is, more or less rigorous experiments may be required.

The appropriate experiments are then carried out by a number of researchers and the results examined. If they support the hypothesis, it gains credence in the scientific community, leading to more and more experimenters working on it, until finally the hypothesis becomes accepted wisdom. If the experiments prove the hypothesis is false, then it will be rejected by the scientific community. The original researcher may suggest modifications to the hypothesis or alternative experiments, but if these too are negative then the idea will "die a death".

Obviously that is highly simplified, but it does give the general idea. Essentially, if an idea can be proved to be true via simple and definitive experiments, then it will become commonly accepted. Even if the idea is highly radical (as with prions), a sufficiently definitive experiment will prove it to be correct. Only where the experiment is extremely difficult to carry out (as with plate tectonics) does it take a long time for the truth to emerge.

The lesson for fuel "saving" devices is this: a technology of such great importance, which can be rigorously proved by repeatable experiments, would not be overlooked by the scientific community for the decades that most of these devices have been around.

For more lessons in "junk science" and how to avoid it, visit The Skeptic's Dictionary.