Certain models can leak oil externally or allow coolant into the combustion chamber due to a faulty head gasket. The head gasket needs to be replaced to correct this problem.
Car Problem Reports
Honda Civic Faulty head gasket may cause oil and coolant leaks
Honda Civic Problem
Engines Affected: 1.5L 4 Cylinder, 1.6L 4 Cylinder
Average Mileage: 150,000 mi (130,000 mi - 180,000 mi)