If you are using street-level routing (accessible to Premium or Premium-Worldwide users) but putting in City/State or ZIP/Postal Codes, it will clean up your route and the mileage may be off. If you are using City/State or ZIP/Postal Codes, then use Highway Only for a clean route and proper mileage. Highway Only is the default for PC*MILER Web Services for those who aren’t a Premium or Premium-Worldwide user.