This took me the longest time to figure out too...if you have the downloaded/CD version, click on the top (near search) for "Forms". This will take you to the actual forms being filed. Then go and ahead and find 2106. On box 3 is the section for rental car, and further down is further vehicle stuff. So you can put travel related values in there, and it updates right away. Then click step by step on top bar again, and voila! It's updated correctly.
Turbotax hasn't fixed it in their "easy" version yet, so just do it the hard way.
