While you probably know him from the “Iron Man” series, Robert Downey Jr. is also known for his awe-inspiring vintage car collection. What sets him apart from other collectors is his form of restoration - he has his petrol-chugging machines transformed into cars feeding on biofuels. One of his pieces in the collection - a 1969 Mercedes-Benz 280SE had its engine swapped to run on 100% vegetable oil. Another car, the 1985 Chevrolet El Camino was powered with solar power on top of the roof, generating green energy.

All of the funds will be transferred to FootPrint Coalition, his nonprofit organization focused on developing technologies that create a cleaner environment. Here’s how the sale works: Contributors visit rdjdreamcars.com and choose the amount you want to contribute to the FootPrint Coalition. Ticket sales have closed for the K-10 pickup because the winner will be chosen soon. The other five winners will be selected, one per month, through July.