Mack

Mack is a character in Cars and Cars 2.

Cars
"Endless days on the road and sleepless nights criss-crossing the country... For some this life would quickly grow old. But not Mack. No sir. Mack knows how important his role is. He's driving Lightning McQueen, the world's fastest racecar. He's part of a team, and everybody knows there's no I in team, just like there's no I in Mack"

Mack has various lines in Cars, despite him only having two in the sequel.

Cars 2
Mack is Lightning McQueen’s trusted long-haul driver, crisscrossing the country from race to race, always with a smile on his grill. After dropping Lightning off in Radiator Springs with his fourth Piston Cup championship trophy, Mack sets off with the rest of the pit crew for a well-deserved vacation. Who knew that Lightning would end up jetting off to a race around the globe in the World Grand Prix?

In the film, he is briefly seen at the beginning when Lightning goes back to Radiator Springs, where he says one of his only two lines. He doesn't accompany him to the World Grand Prix due to being on vacation. At the end he talks with Lizzie and says the other of his only two lines of the movie.

His lines in the sequel are "Oh, these best friend greetings all get longer every year," and "Oh, those 2 are perfect for each other."

Trivia

 * Mack is a 1980s-era Mack Super-Liner truck.
 * When Mack watches the Cars-parodies of previous Pixar movies, he thought whoever did the voice of Hamm, P.T. Flea, and the Yeti as cars is one great actor until he realized they used the same voice actor in all movies and wonders "what kind of a cut-rate production is this?". This is a reference to John Ratzenberger (who portrays Mack) having to portray at least one character in every Pixar movie.
 * In Cars 2, he has the least amount of dialogue out of all of John Ratzenberger's roles, because he only had 2 lines.
 * The sail on Mack's roof actually resembles a trucker cap, which is often worn by many truck drivers in real life. This is extremely noticeable due to the prominent visor protruding above his windshield (eyes).
 * For some reason, Mack and Lizzie are the only inhabitants of Radiator Springs that did not participate in the final battle against the Lemons in England at the end of the sequel. Also, Mack and Lizzie are the only inhabitants of Radiator Springs who did not come to England. Fillmore also does not participate in the London battle, probably because he is a pacifist.
 * For some reason, the dog-shaped hood ornament on Mack's hood isn't car-ified.

From Cars