hmmm. during the winter's we dont wash it. the water tends to freeze the door seals since up here in ND, it usually stays below freezing from november to march.
havent washed the legacy since i bought it except the front end of bugs, but its silver so meh. doesnt look that much different dirty than clean. during the spring/summer/fall the winds up here pretty much blow dust/dirt back onto the car that you have a film by the next day.