Ben (while in human form) eats a fried chicken leg - along with half the bone. He's not capable of that.
Ben uses XLR8 to return the Rust Bucket to normal. Upgrade would seem the better choice for returning it to normal in one fluid, brief motion. Either way, the speed at which Ben, as XLR8, changes the Rust Bucket back suggests a technical knowledge of vehicular repair Ben wouldn't seem inclined to possess.