In Pixar's Cars, who is the tow truck named Mater's best friend?

In Pixar's Cars, Mater's best friend is Lightning McQueen.

Mater is the rusty tow truck who lives in Radiator Springs and first meets Lightning after the race car is stranded there. Their friendship develops as Mater introduces Lightning to the town, helps him understand its residents and shares local adventures. By the end of the film, Lightning chooses friendship and community over immediately leaving for the championship race.

The relationship remains central in Cars 2 and Cars 3. Mater accompanies Lightning on international espionage adventures in Cars 2 and supports him during the later racing story. Although Doc Hudson becomes Lightning's mentor and Sally is his romantic partner, neither is Mater's best friend. The specific friendship pairing is Mater and Lightning McQueen.