"Transformations", David Barr Kirtley

SS RoF (Realms of Fantasy) December 2007 – science fantasy
<<- Realms of Fantasy December 2007 interior illustration by Rob Johnson for "Transformations"
Carrus, disguised as a red sports car, meets a boy named Alex. Carrus is a robotic soldier assigned to Earth on a covert mission during a space war. Alex likes Carrus because he is an awesome talking car that can transform himself into a huge robotic infantryman. Lonely Carrus makes a friend whom he visits over a period of years.

Alex as a young boy, teenager, and middle-aged man gets to play with a really cool car that only he knows about. This isn't a first contact or robot war story, it's more or less a guy's automotive fantasy dream. Sort of fun.