I've spent the last month or so trying on the various name suggestions for the Fiat, plus a few ideas of my own. For example, Enzo is a really cool name that seems to go with the heritage and the color, but at only 100 hp, I just couldn't tell people the Fiat's name was Enzo with a straight face.
In the end, the name that grew on me and became natural was Guido. Parsla suggested this with all of the great reasons that it works.
1) Guido is the first-person, present conjugation of the Italian verb guidare ("to drive"). Naturally, I didn't know that, but Parsla did.
2) Guido was Luigi's sidekick in the original movie "Cars"
3) Slang for a working class Italian-American
The Fiat is definitely a working class Italian-American, but also Mexican. And it definitely loves to drive.
I decided to formalize this with a portrait in front of the Guidobono Concrete company. Now, Guidobono is actually a name of long standing, but if you take it apart and use some linguistic license, Guido bono can be interpreted as "certified Guido". So that's what my little red Fiat is, a certified Guido.