Assuming the Chosen One does not kill T-Ray in the process of recovering the Highwayman, T-Ray can be contracted to perform upgrades on the car. Initially the only upgrade available is increased trunk space for $500 ($300 if the Chosen passes a Barter check), however, upon completion of the game's main story line one may opt to have T-Ray install grav plates to significantly reduce the car's fuel consumption.
After paying for the car and upgrades T-Ray will say that he has batteries in stock, but if bartered with he only sells Jimmy Hats, a shotgun and a cosmetics case.
If slept with to recover the car, and seduced again for the upgrade, he will say he "just gave [the female Chosen One] sweet love five minutes ago". This is a reference to Chef, a character from the show South Park, during the episode, 'Weight Gain 4000'.