A customer checking out the new Jeep Cherokee might be more intrigued by the novel nine-speed transmission than by what's inside the air conditioner compressor.

But the refrigerant flowing through the veins of the Cherokee's air conditioner, a formulation called 1234yf, might be just as crucial as the gearbox to Chrysler's strategy for satisfying strict new environmental rules in the United States and Europe.

Auto companies are moving quickly to adopt 1234yf, despite its higher costs and a safety scare that raised concerns about possible toxic leaks. Regulators like it because it leads to lower greenhouse gas emissions than the chemical used in most vehicles today, which is called R134A.

Another big incentive: Vehicles that use the new refrigerant, like the Cherokee, qualify for tradable credits from the EPA, helping them comply with new fuel economy and greenhouse gas standards that will double to the equivalent of 54.5 mpg by 2025.

"We're a strong supporter of 1234yf as the new environmentally friendly refrigerant for the industry," said Michael Rinaldi, a senior manager for HVAC systems at Chrysler.

Until recently, that switch seemed threatened by Daimler's objections.

The automaker stunned the industry in September 2012 with tests showing 1234yf catching fire and spewing toxic gas into the cabin of a Mercedes-Benz B-class hatchback. But the storm cloud now seems to have passed.

A study released in April by SAE International, with participation from the Detroit 3 and several Asian automakers, concluded that 1234yf is "safe and effective," and went so far as to suggest that Daimler may have designed its tests to show a problem.

A second analysis, released in August by the German environmental regulator KBA, concluded the new refrigerant is somewhat riskier than R134A, but not dangerous.

Daimler's claims "caused everyone in the industry to pause and take stock, in case something had been missed," said Ken Gayer, vice president and general manager of Honeywell Fluorine Products, which holds the patents on the new refrigerant along with DuPont. "We feel that the concerns over the use of 1234yf have been significantly assuaged through all of these findings."

At this point, half a million vehicles on the road worldwide use 1234yf, including the Cadillac XTS and Honda Fit EV in U.S. showrooms. That number will increase rapidly in 2017, when a European mandate takes effect, so Honeywell is ramping up production. Honeywell said this month that together with its suppliers, it will invest $300 million to produce 1234yf at its chemical manufacturing facility in Geismar, La., starting in 2016.