I am in possession of an 89 Mazda 626 with an automatic transmission and a 2.2L engine, which does not possess a turbocharger. Upon purchasing the vehicle, I made the disconcerting observation of oil presence inside the radiator system.Based on my assumption that the issue lay with the head gasket, I proceeded to replace the gasket, conduct a pressure test on the cylinder head, and afterwards reassemble the components. It is worth noting that despite the absence of any indications of water or coolant contamination in the oil, the engine exhibited satisfactory compression levels and operated rather smoothly. At now, I own a very functional automobile that has undergone repairs, namely the replacement of the head gasket, which has resulted in the presence of oil inside the coolant system. It is important to highlight that the vehicle is functioning well, with a stable temperature and no presence of coolant in the oil. Furthermore, this observation was made two days after the completion of repairs. The oil in the overflow container is not mixed or frothy, and the liquid being discharged from the radiator overflow seems to be rather clean. The auditory perception of fluid being drawn back into the radiator via the top hose suggests the possibility of oil being entrained with the coolant during the cooling process. Assistance in this matter would be highly appreciated.