Eating in your car may save time, but what you gobble down could hurt your car's value, according to Kelley Blue Book.

Sixty percent of owners let people eat in the their vehicles, according to a survey by Kelley and Taco Bell. Only 34 percent said cleanliness was the top factor in long-term value.

That could be costly, the group said in a news release.

"Cars in excellent condition and appearance -- both inside and outside -- can be valued thousands of dollars higher than those in good or fair condition," said R. Nerad, executive editorial director and market analyst for Kelley Blue Book.

The survey found that people who allow eating in their vehicle were less concerned with their vehicle's overall appearance, ranking all vehicle attributes lower than those who don't allow eating in their car.

Thirty-four percent of people in the survey said burgers and fries were the messiest food they have eaten in their car.