With the engine running, he can see on-screen how much fuel should be injected given X throttle pressure or Y coolant temperature.

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Eco mode slows the throttle and dampens the AC to save fuel but is noticeably more sluggish than the sport or even the normal settings.

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Meanwhile, the feds' fuel-economy administrators are currently operating at a dead run trying to keep up with a host of new, highly digitized fuel-saving technologies, such as "Eco" throttle mapping and stop-start (the engine cuts out as the vehicle coasts or stops), which were practically invented to hack the EPA testing cycle.

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In Eco mode, parameters such as the throttle map and air conditioning are controlled for minimal fuel and electrical consumption.

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Throttle them back even a little, and the amount of energy obtained for each barrel of fuel burned falls sharply.

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