The Supreme Court ruled in January 2011, that the Means Test Vehicle Ownership allowance is contingent on existence of loan or lease obligation. In other words, if you own a vehicle "free and clear" and are not making any payments, you cannot claim the ownership deduction. (Ransom v. FIA Card Services, __ U.S. ___ (S.Ct 2011 ) )
Before the Supreme Court settled the issue, lower courts were split on this question.
Note that lower court cases that deny the allowance often mention that debtors can claim a $200 extra operation deduction for vehicles over six years old with more than 75K miles (based on the IRS practice of doing the same).