Merzario began his career as a test driver with works Fiat Abarths, subsequently participating to GT racing and European mountain-climb events.

[1] In 1969 he won the Mugello Grand Prix in a 2-litre Abarth ahead of a field which included Nino Vaccarella and Andrea de Adamich.

[1] Merzario made his Formula One debut in 1972, and became one of the few drivers to score points at their first race by finishing in sixth place in the British Grand Prix at Brands Hatch.

37 years later, in an interview with BBC Radio 5 linked to the release of Rush, Lauda stated that "Merzario jumped into the fire and, alone, pulled me out of the wreckage so I survived… he really saved my life there, because a couple of seconds more I would have never made it.

"[3] Six weeks later after the incident, at the Italian Grand Prix, Lauda returned to race again and presented his gold Rolex wristwatch to Merzario in gratitude for saving his life.

[1] Merzario continued with his own chassis for two seasons, but results were very poor; the team's cars did not qualify on the majority of occasions, and often retired from the races they did start.

Merzario began his career with Abarth in GT racing and mountain climbs;[1] he also won the Sardinia Rally in 1963 in an Alfa Romeo Giulietta.