A custom 1977 Mercedes-Benz Unimog once owned by Arnold Schwarzenegger is headed to the Barrett-Jackson auction next month in Scottsdale, Arizona.

Schwarzenegger is a large man who, naturally, likes his vehicles just as large. When it was time to let his noted Humvee fall by the wayside, the Austrian-born muscle man stepped up. It was time for something new, something like a Unimog.

He didn't own the Unimog since new, though. He only took delivery in 2012, after the vehicle was fully restored, modified, and upgraded by Unimog specialist Merex Mertec in Gaggenau, Germany, to the actor and former politician's specifications.

Among the upgrades are 22-inch wheels shod with Michelin XZL 445/65 tires, air suspension, a trailer brake system, a roll bar, Hella lights, and a custom bed. Schwarzenegger's signature also sits atop the center stack.

Arnold Schwarzenegger's 1977 Mercedes-Benz Unimog

Arnold Schwarzenegger's 1977 Mercedes-Benz Unimog

Schwarzenegger didn't own the vehicle for long, though. It was already listed for sale on a German classifieds website as early as 2014.

That might have been due to the vehicle not gelling with the green policies Schwarzenegger was promoting during his time as "Governator" of California. The powertrain in his Unimog, a turbodiesel 6.4-liter inline-6 delivering 320 hp, isn't exactly the cleanest of lumps. Designed more for commercial use, it only complies with Euro 3 emissions regulations that came into force in 2000, and permits more than ten times the harmful particulate matter that current European regulations allow.

After Schwarzenegger's ownership, the Unimog traded hands several times among new owners in the U.S. It is lot number 1297 at the Barrett-Jackson Scottsdale auction that runs Jan. 20-28.