Can an oil with a better standard be poured into the engine of a car with a lower standard requirement?

    When buying a car, we often wonder what is its actual mileage and what oil was applied by the previous user. The answers to both questions should be given by the former owner, but they often do not know or are simply not interested in them.
    Unfortunately, this type of situation can cause problems to the new owner who, in good faith, basing on the vehicle mileage and recommendations of the manufacturer, pours premium quality oil recommended for the model. If the mileage was real, and the oil previously used was of a similar class and was regularly changed, we can be confident about our new acquisition. Otherwise - high mileage and operating the engine at low-grade oil - pouring oil of worse quality can cost us dearly.
    Generally, if the car engine is filled with mineral oil, it should not be changed for a synthetic or a semisynthetic oil. If the engine is operated at a semisynthetic oil, we can safely replace it with a mineral oil. A synthetic product can be replaced by a synthetic or a semi-synthetic mineral oil, provided that the levels of quality and viscosity are as required.
    So, what are the dangers for the drive unit resulting from the change of mineral oil to a synthetic product? Well, mineral oil creates a slightly thicker oil film on the more worn engine parts of an exploited engine with high mileage. In addition, mineral oils, especially those of lower quality grades, contain much less additives responsible for keeping the engine pure than synthetic oils. This difference may cause a threat to the engine which is used only at a low-grade mineral or a semisynthetic oil. Changing a mineral oil to a synthetic oil can cause dissolution and leaching of the existing deposits and carbon deposits in the engine. There may, therefore, appear clearances at the engine worn parts which in turn will cause accelerated wearing. Additionally, there is a risk of oil leakage from the engine due to the dissolved deposits around the engine seals.
    Cars that were operated on oils recommended by manufacturers and with changes on a regular basis and in accordance with the indications of the service should not be exposed to this type of danger, even when using the oil meeting the standards higher than those recommended. An example would be the use of oil of quality grade according to API SM for a gasoline engine for which an API SL oil is recommended.
    However, in the case where oil quality requirements are determined by manufacturers by means of their own standards and specifications, it is recommended not to use oils of similar viscosity and qualitative parameters that do not meet specific standards required by the manufacturer.