Chugging French fry oil isn’t exactly advisable for humans, but that’s exactly what keeps this old train running. The Grand Canyon Railway’s Locomotive No. 4960, AKA The Iron Horse, a steam engine built in 1923, uses waste vegetable oil for fuel.

The Grand Canyon Railway is one of the few railroads in the US to use a restored steam engine for long journeys, and it’s the first in the country to use recycled vegetable oil as fuel. The idea came about thanks to the railway’s management staff, who were inspired by carmakers running vehicles on waste vegetable oil. Deciding to apply the same system to a steam engine, they realized that it worked exceedingly well, allowing the nearly 100-year-old engine to run carbon-neutral and produce far fewer emissions than a diesel engine. The water used by the boilers is also sustainable; a press release explains that “boilers contain reclaimed rain and snowmelt (when Mother Nature allows) collected during the winter and Northern Arizona’s rainy season for steam.”

From April to October, on eight specific dates, passengers are able to ride this historic train on a 65-mile journey from Williams, Arizona, to the South Rim of the Grand Canyon.

The railway invites visitors to “Enhance your Grand Canyon experience with an entertaining train ride featuring western musicians and cowboy characters on vintage rail cars.” There are many packages that include lodging at the Grand Canyon Railway Hotel and inside Grand Canyon National Park on offer.