You might find that using a roof rack makes for a roomier road trip, but it comes at a cost.

The extra wind resistance caused by packing your gear on the roof ... read full tip

You might find that using a roof rack makes for a roomier road trip, but it comes at a cost.

The extra wind resistance caused by packing your gear on the roof can decrease your fuel-efficiency by about 5 percent.

If you're planning a cross-country vacation, you could save an entire tank of gas-about $30-$50-by leaving the roof-rack at home and packing-up the trunk instead.

If an additional 0.1 percent of the long-distance miles driven each year were in vehicles without roof racks, an estimated $5.2 million worth of gas could be saved per year-enough to buy 65,000 annual National Park passes for road-trippers across the country.