I know we have good data for some of these techniques, but has anyone measured (a-b-a) the effect for each of them? I am especially interested in rear wheel covers and smooth hubcaps, as these might be something SWMBO might go for.

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Best tank ever: 72.1 mpg in February 2005, Seattle to S.F.
New personnal best 'all-city' tank June '08 ... 61.9 mpg!
Thanks to 'pulse-n-glide' technique.