P.E. yes I've heard it does reduce mileage by a couple mpg's maybe? The ALDA on my car still has the cap, so I asssume it's never been done before. I might try it sometime, but I'm pretty satified as is since I average 18mpg 75% city.
Thanks
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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