The date (month/year) of manufacture should be stamped on a plate (for U.S. vehicles anyway) which is on the driver-side door frame.

According to various hits on the 'net, The ranges I found indicated you can wax a new car anywhere from right away to 21 days after you bring it home. I'd say go ahead and wax it in another week or two if you feel unsure or right away if you find that the date of mfg is over a month ago.

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Stay the Trail!