I tried that once...eking out every ounce of mileage during a trip. It was very hard work! Frankly until gas hits $8 a gallon, I going to just drive it and be happy with my usual 14.9 mpg.

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BMWCCA Chapter President, Hawaii Chapter (fmr)
03' X5 4.4i, 02' MCoupe, 99' MCoupe (sold), 88' M3, 01' E39 M5