Car & Driver tested 15 Wonder products, each of which would yield fuel savings of up to 25%.
And do you know what? Of the fifteen, 14 did not work. The fifteenth had never arrived after ordering - and payment.
The wonderful electronics in one of the toppers consisted of .... A LED.
For 1500 dollars there was also the possibility to buy a hydrogen set: a bottle of water underneath the hood. From that bottle a hose ran to the air filter and there were two wires in the bottle that were connected to the battery ...
Economical driving is only between the ears and in the right foot ...
Pity