Clarence Ditlow speaks to reporters in 1994 about a government settlement with General Motors over the auto company’s pickup trucks. (J. Scott Applewhite/AP)

Clarence M. Ditlow III, a consumer advocate who helped force automakers to install lifesaving features such as air bags and to remove millions of defective vehicles from the road during a four-decade campaign for auto safety, died Nov. 10 at a hospital in Washington. He was 72.

The cause was colon cancer, said his wife, Marilyn Herman. Since 1976, Mr. Ditlow had served as executive director of the Center for Auto Safety, a Washington-based nonprofit organization founded by Ralph Nader and the Consumers Union advocacy group.

The son of a Chevrolet service manager, Mr. Ditlow pursued dual training in engineering and the law, joined Nader’s group of activists as a young lawyer and became what the New York Times once called the “splinter” that the car industry could not “remove from its thumb.”

Under Mr. Ditlow’s leadership — on a shoestring budget and through methods both celebrated and criticized — the Center for Auto Safety battled lawmakers as well as car manufacturers, winning changes in regulatory and business practices that were credited with saving thousands of lives.

He was “one of the chief watchdogs” of the National Highway Traffic Safety Administration and the auto industry, said Nader, whose 1965 book “Unsafe at Any Speed” helped incite outrage over what Nader described as the auto industry’s willingness to trade safety for profit. Nader described Mr. Ditlow as a “full-time citizen for motorist safety.”

Among the center’s most significant early victories was the recall in 1972 of 6.7 million Chevrolets with defective engine mounts, a flaw that could cause the accelerator to jam and the brakes to malfunction. In 1978, the group helped force the recall of 14.5 million Firestone 500 tires after the blowout-prone model was linked to dozens of deaths and injuries.

The same year, again with pressure from the Center for Auto Safety, Ford recalled 1.5 million Pintos and Mercury Bobcats at risk of fuel tank fires. A similar problem surfaced years later in Chrysler Jeeps; 2.5 million of them were recalled in 2013.

“He makes ’em; we recall ’em,” Mr. Ditlow had told the Times in 1991, referring to then-Chrysler Chairman Lee A. Iacocca. “We have a standing offer to stop our opposition when they stop making bad cars.”

Few if any major automakers escaped the center’s scrutiny. In a 2014 settlement with the Justice Department, Toyota admitted to having deceived the public about the risk of sudden acceleration in certain vehicles. The company was fined $1.2 billion — reportedly the largest criminal penalty ever imposed on an automaker by the United States.

The next year, General Motors agreed to pay a $900 million fine in a settlement with the Justice Department after the exposure of an ignition-switch defect, also uncovered with help from Mr. Ditlow’s group, that was reportedly linked to 174 deaths.

Mr. Ditlow cited the requirement of dual frontal air bags, effective for all cars since the 1998 model year, as the “biggest single advance” in automotive safety. The devices have saved more than 42,000 lives, according to an estimate from NHTSA.

But even air bags sometimes presented problems: In 2015, in part through the efforts of Mr. Ditlow’s group, Takata air bags in nearly 34 million vehicles were recalled after the products were sometimes shown to discharge shrapnel when they deployed. The Washington Post reported that it was “expected to be the biggest recall of any consumer product in U.S. history.”

In pursuing their cause, Mr. Ditlow and his colleagues assembled a database of thousands of consumer complaints, then mined it to discern patterns. They also tracked lawsuits against automakers, looking for settlements that raised red flags.

At times, the group drew criticism for what some federal regulators considered crying “wolf,” undermining government oversight efforts with its own watchdog activities and working too closely with product liability lawyers, whom Mr. Ditlow considered useful partners in his cause.

The Center for Auto Safety figured prominently in a high-profile, highly fraught controversy in the 1990s over the recall of GM pickup trucks with “side saddle” fuel tanks. The center described the vehicles as “rolling firebombs,” prone to catching fire in the event of side collision. GM claimed that critics had engaged in a campaign to “sensationalize and prejudice the record.”

Feeding the controversy was a report in which the TV newsmagazine “Dateline NBC” rigged a fiery explosion involving one of the vehicles. The show’s anchors later apologized for the breach of journalistic ethics and announced a settlement with GM.

Amid the investigation of the trucks, a former GM lawyer sued Mr. Ditlow for libel and slander, accusing the consumer advocate of falsely claiming that the lawyer had ordered the shredding of company documents related to the trucks. The case ended in a settlement, with the Center for Auto Safety’s insurer paying a reported $500,000.

A judge assessed Mr. Ditlow and his lawyer $54,000 in fines and damages after they “brazenly ignored the court’s order” by releasing a sealed deposition to other lawyers engaged in a lawsuit against GM.

In 1994, the federal government and GM reached a settlement in which the government ended a recall investigation and GM agreed to contribute more than $51 million to auto safety initiatives. Mr. Ditlow did not relinquish his campaign; nearly a decade later, he railed against the design as the “worst auto crash fire defect in the history of the U.S. Department of Transportation.”

Clarence Mintzer Ditlow III was born Jan. 26, 1944, in Louisville, Ga., and grew up in Camp Hill, Pa. He was inspired to work as a consumer advocate during chemical engineering studies at Lehigh University in Bethlehem, Pa., where he graduated in 1965. As a student he visited a steel plant, he told the Times, where workers had little protection against industrial accidents.

He received a law degree from Georgetown University in 1970 and a master’s degree in environmental law from Harvard University the following year. He worked with Nader’s Public Interest Research Group before becoming executive director of the Center for Auto Safety, which was established in 1970.

Mr. Ditlow testified before federal officials and otherwise lobbied on matters including car warranties, fuel-economy standards and “lemon laws” to help buyers of flawed vehicles. The Center for Auto Safety was credited with helping enact such laws in 50 states.

With Nader and others, he helped write editions of “Lemon Book,” a guide for unlucky car owners seeking recourse. His other publications included “Little Secrets of the Auto Industry: Hidden Warranties Cost Billions of Dollars” (1994), written with Ray Gold.

Besides his wife, of Washington, survivors include a sister.

Mr. Ditlow drove a variety of Chevrolets over the years, including the Geo Prizm, the Nova and, most recently, a hybrid Monte Carlo. (He also rode the Washington subway after he was struck by a car while riding his bicycle.)

He said he was hopeful that advances in technology would improve auto safety by automatically alerting drivers to potential dangers.

“We have a number of accidents each year because of driver inattention,” he told the Times in 1997. “You can tell from the movement of the steering wheel whether someone’s getting drowsy, and you can build in an audible alert that says, ‘Wake up!’ Heck, I just had Dr. Ruth tell me to buckle my seat belts in my New York cab yesterday.”

An earlier version of this article incorrectly reported that Mr. Ditlow succeeded Ralph Nader as executive director of the Center for Auto Safety. Nader was a co-founder of the organization, not an executive director.