This seems quite good but I haven't used it yet so cannot really comment. (admin you may wish to move it to another forum - i'm not sure)
It's £50 fromhttp://www.amazinghealth.co.uk/Save_money_on_your%20car_fuel.htm
ADVERT: Want to save money on your petrol and save the environment too?
Motoflow is designed to condition the fuel before combustion. Fuel exposed to a magnetic field in this way carries more energy and mixes more readily with air resulting in a more complete combustion. This means more energy and less waste produced from the same amount of fuel.
Tests show up to 20% reduction in costs of fuel, better performance and less pollution.http://www.amazinghealth.co.uk/Motoflow%202.jpg
I'd appreciate any comments as well.