I find that my engine is off enough of the time, I barely get enough charge. I get 14.x volts when the engine is running, but that's 1/2 or less of the driving time. This time of year, with headlights a necessary evil, I'm happy to keep it charged enough to crank the starter. No way I can/will change the pulley on my alternator.
It's close, though. LED's would probably tip the balance just enough.
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11-mile commute: 100 mpg - - - Tank: 90.2 mpg / 1191 miles
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