Presumably Steed's first car in The Avengers is a Rolls Royce in series 1 and he obviously used another more downmarket vehicle too, when the Rolls Royce was "too showy". (Please Don't Feed the Animals)
Then he drove four different cars in series 2 and 3: a Greyhound, followed by a Triumph Herald, an Alvis, a Lagonda.
A Vauxhall and several different Bentleys are his cars in series 4 and 5.
He drove a Bentley and two different Rolls Royces again in series 6.

During The New Avengers Steed's cars were a Jaguar and Rovers.
Rolls Royces


Triumph Herald

Alvis Tourer




TNA Jaguar and Rovers

Information about the cars (especially the Bentley and Rolls Royces from series 6) are based on:

Cars used in the TV series The Avengers

Vintage Bentley.org
Fanzine articles about John Steed's driving and his cars

Geoff Barlow: Motoring Avengers Style, in: Stay Tuned, Volume 1, Issue 1, pages 23 -26
fictional information about how John Steed learned to drive and why he likes the Bentley so much.
Steed's Cars
Damaged Cars

Destroyed Cars

Other Vehicles used by Steed

Which cars used Steed when?

Which Bentley appeared in what episode?

Patrick Macnee's Jaguar in The Avengers

Model Cars