4 percent from the same month in 2012, the Society of Indian Automobile Manufacturers (SIAM) said.
The car market, seen as an important guide to India's overall economic health, has recorded a fall in sales for an unprecedented nine consecutive months.
"There's general gloom with the economic slowdown, high interest rates and high fuel costs," SIAM's deputy director general Sugato Sen told AFP.
"It's all deterring buyers," he said.
The data is the latest in a string of grim figures underscoring the weak state of Asia's third-largest economy.
The market's downturn is in sharp contrast to the previous decade when car sales grew by 20 to 30 percent -- prompting foreign giants from Ford to Volkswagen to make a beeline for the country as they sought to boost sales globally. Total bus and truck sales -- another important economic health barometer -- plunged in July by 14.
9 percent to 55,301 units from a year ago.
Meanwhile,