Platinum and palladium haven’t been acting much like sister metals in the wake of the Volkswagen scandal, even though both are widely used in vehicle production, but there is a good reason for that.

Both metals are used in catalytic converters, which help control harmful emissions coming from car exhausts, but “platinum is notably used for diesel vehicles and palladium for gasoline vehicles,” said Mike McGlone, director of research for ETF Securities.

“The VW scandal has contributed to negative sentiment for diesel vehicles, probably benefiting gasoline,” he said.

The U.S. Environmental Protection Agency on Friday accused Volkswagen AG’s VOW, +1.04% Volkswagen and Audi divisions of violating the Clean Air Act, alleging the German car maker equipped certain diesel cars sold in the U.S. with software used to cheat pollution standards. Read: Volkswagen emissions scandal could be just the beginning, Wall Street says

On Wednesday, platinum prices US:PLV5 settled at their lowest level since 2009, while palladium US:PAZ5 soared to its highest price in two months.

“Before the VW scandal, diesel vehicle interest in the world’s largest market, Europe, was diminishing, notably due to poor emissions and the declining price for petroleum,” said McGlone.

The scandal has aggravated that trend, and it may be “diminishing demand for diesel vehicles and increasing demand for gasoline vehicles,” so there is likely more need for more palladium, he said, adding that very little platinum is used in gasoline vehicles.

Diesel engines operate at lower temperatures than gasoline engines and platinum is better suited as a catalyst to reduce harmful emissions at lower temperatures, according to Stillwater Palladium.

China, meanwhile, has been pledging to reduce pollutions, including harmful vehicle emissions.

Smaller gasoline vehicles are predominant in China, which could mean more palladium use, said McGlone.

The amount of palladium used per vehicle needs to be increased to help reduce emissions, or these gasoline-powered vehicles need to be replaced with electric ones “to be on par with most Western manufacturers,” he said.

And that may bring a new shine to palladium investors returns.