Вот наткнулся на интересную штутчку 
 http://www.priceangels.com/NEO_SOCKET_Fuel_Economizer_for_Car-Save_Fuel_Gas_10_-30__12V__p29342.html
http://www.priceangels.com/NEO_SOCKET_Fuel_Economizer_for_Car-Save_Fuel_Gas_10_-30__12V__p29342.html Принцип работы такой:
The Neosocket is a new application of an old technology. Basically, it acts 
like a small battery that helps your car's electrical system perform better. 
The small device is fitted with a capacitor that once plugged in to your 12v 
adapter is instantly connected to the car's main electrical system. 
(capacitors are also commonly used to power the electronic flash in cameras)
The capacitor first charges and then discharges the stored electricity 
(voltage) when there is a heavy energy demand from the alternator. Heavy 
energy demand (reduced voltage) is caused by using any electrical accessory 
in your car including lights, windshield wipers, air conditioning, stereo or 
any combination of them.
Instead of the alternator and battery having to work overtime, Neosocket 
supplements the required voltage to reduce the load on the electrical system 
from any accessory that is being used. The reduced electrical demand frees 
up energy that can be better used to deliver a more constant and steady 
supply of electricity to the spark plugs and ignition system.
The result is a more efficient and complete combustion of the gasoline which 
will improve you gas mileage and produce cleaner emissions. You will also 
get better horse power, acceleration, and a smoother running engine despite 
daily driving conditions.
The fact is that fuel mileage will fluctuate in any car due to driving 
habits, lack of maintenance, traffic conditions and many other factors. All 
these factors will rob the fuel efficiency your car was meant to achieve. 
The main purpose of Neosocket is to help your engine consistently maintain 
its designed fuel efficiency despite of all these unpredictable situations.
Тут отзывы есть 
http://www.focalprice.com/reviewdetail_ER917L.htmlА тут обсуждение на субару форуме 
http://subaruland.ru/forum/threads/fuel-economizer.2115/Кто что думает? Разводилово?
Всего 5 баксов с бесплатной доставкой.