What is the most amount of hot wheels cars collected?

Michael Zarnock USA has held 2 Guinness World Records for his Hot Wheels Collection.

2003 - 3,711 different Hot Wheels cars

2007 - 8,128 different Hot Wheels cars.

Currently (2012) has over 12,000 different Hot Wheels cars.

He has over 20,000 cars in his collection....