Titanic star Leonardo DiCaprio has taken his relationship with girlfriend Blake Lively a step further by buying her an eco-friendly motor.DiCaprio, 36, who is known for pushing green causes, is said to have been horrified to learn Lively, 23, was driving a Range Rover, the Sun reported.So he has given the actress a 25,000 pounds black Prius.The hybrid petrol-electric car gets 50 miles to the gallon compared to 20 for a Range Rover.