Automotive engines on the current market are available in several common designs. Nearly all four-cylinder engines have an inline layout. Most six-cylinder and eight-cylinder engines have V-shaped configurations. Subaru prefers to use a horizontally opposed assembly under the hood. Since the 1960s, the patented Boxer engine has been installed in nearly all of the company's cars. Throughout the decades, this auto manufacturer has made significant improvements in the performance of this unique powertrain.