i have noticed lately that the highway mileage of my 2010 tucson hyundai has fallen from 31-32 mpg on highway drive to 26.5 mpg. auto has 71,000 total mileage? any ideas.

 

Are we talking just one tankfull or over multiple tanks? Was it all highway driving or did you have some city driving? Are you basing the MPG off the computer or manual calculation? MPG will drop as the weather gets colder. That's normal.