A
piston engine which has at least one dry-running
piston-cylinder unit. It has a first housing (1), at least one cylinder arranged in or on the first housing (1) in which a
piston is reciprocably arranged. The piston-cylinder unit further has a first
crankshaft (4) and a second
crankshaft (5), the first and second crankshafts (4, 5) being arranged parallel to each other and synchronously rotating in opposite directions. The axes of rotation (X, X′) of the crankshafts (4, 5) are arranged parallel to a center plane (Z) of the cylinder, and they are laterally offset relative thereto. First and second piston rods (6, 7) are pivotally connected to piston (3). The first
piston rod (6) has a first end pivotally connected to piston (3) and a second end connected to a
crank pin (40) of the first
crankshaft (4). The second
piston rod (7) has a first end that is pivotally connected to piston (3) and a second end that is pivotally connected to a
crank pin (50) of the second crankshaft (5). The crankshafts (4, 5) are journalled in a second housing (8) which holds a
lubricant. The crankshafts are arranged so that a respective first end of each crankshaft (4, 5) sealingly projects from second housing (8) to prevent the escape of
lubricant into first housing (1). The respective piston rods (6, 7) are arranged in the first housing (1) outside second housing (8).