Car (South Africa) - - TECH -

With the cur­rent hike in the price of petrol, I am con­sid­er­ing pur­chas­ing a fuel-sav­ing de­vice. I know how to save fuel by chang­ing my driv­ing style but I need an ad­di­tional sav­ing. There are sev­eral de­vices in the mar­ket and they prom­ise sig­nif­i­cant re­sults and even list favourable ref­er­ences on their web­sites. I am a bit scep­ti­cal but, in dif­fi­cult fi­nan­cial times, I am tempted to try one. HENDRIK LOUW Parow

Un­for­tu­nately, when the price of fuel in­creases, there is al­ways a spike in the num­ber of ad­ver­tise­ments of fuel-sav­ing de­vices to en­tice mo­torists. CAR mag­a­zine con­ducted sci­en­tific test­ing on a num­ber of these de­vices for the May 2016 is­sue (search Fuel-sav­ing de­vices busted! on Car­mag.co.za). In essence, these are all scams to con peo­ple out of their money.

It takes only a ba­sic un­der­stand­ing of en­gi­neer­ing to re­alise these de­vices can­not work. Most of them tar­get the com­bus­tion process by al­ter­ing the air­flow or some­how mod­i­fy­ing the fuel en­ter­ing the en­gine (the usual sus­pects in­clude mag­nets, air­flow mod­i­fiers and even fuel ad­di­tives). The com­bus­tion process in a mod­ern in­ter­nal­com­bus­tion en­gine is al­ready ca­pa­ble of ex­tract­ing more than 99% of the en­ergy in the fuel. There­fore, there is very lit­tle room for im­prove­ment.

Many favourable ref­er­ences are writ­ten in good faith (the placebo ef­fect is well doc­u­mented). Folks pur­chase a prod­uct and ex­pect it to work. Sub­con­sciously, they adapt their driv­ing style and, as a re­sult, there is a sud­den drop in fuel con­sump­tion (driv­ing style has by far the big­gest in­flu­ence on fuel econ­omy). Given time, old habits re­turn and the “ben­e­fit” is lost.

Steer clear of these de­vices.

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