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Use of more viscous oil in high mileage engines is not technically recommended, according to specialist.
The replacement of the manufacturer-recommended oil with more viscous versions continues to be a practice found in some workshops, especially in vehicles with high mileage. However, specialists state that the change does not resolve internal engine wear and can still bring negative impacts to the functioning of the mechanical assembly.
In the segment “the mechanic answers,” a specialist clarifies the doubt of a Toyota Corolla owner who claims to have been advised to change the synthetic oil 5W30 to 10W40 after the car surpassed 150,000 km. The justification is usually an attempt to “compensate for clearances” caused by the natural wear of the engine over time.
According to Cleyton André, technical consultant of Revista O Mecânico, the alteration has no technical basis when there is no provision from the vehicle manufacturer itself.
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Manufacturer-recommended oil should be maintained
According to the specialist, the choice of lubricant is part of the original engine development. This means that the indicated viscosity is not defined randomly.
Each project considers specific factors, including:
- Operating temperature
- Internal engine materials
- Part tolerances
- Lubricant circulation
- Additive package
During participation in the segment Mechanic Answers, on YouTube, Cleyton André criticized the practice of thickening the oil in more used engines.
According to him: “It never made sense and it won’t make sense today.”
The consultant also classified the recommendation as incompatible with the correct principles of mechanical preservation.
Change in oil can affect lubrication
The specialist explains that modifying the viscosity without authorization provided in the manual can directly interfere with the engine’s operation.
This is because the oil plays an important role not only in lubrication but also in thermal control and internal circulation of the system.
According to Cleyton André: “Maintaining the specifications recommended by the manufacturer is extremely important.”
He emphasizes that the engineers responsible for the vehicle’s development define in advance which type of oil should be used under different operating conditions.
When the manufacturer allows more than one option
In some models, manufacturers provide more than one viscosity specification. In these cases, alternative use is officially foreseen.
Outside of this situation, however, the specialist states that there is no technical justification for changing the lubricant just because of high mileage.
The recommendation, according to him, should follow exclusively what is described in the vehicle’s manual.
Mechanical problems are not solved with thicker oil
The idea of using thicker oil to hide internal wear is still common in part of the automotive sector. However, the consultant states that this practice does not correct mechanical clearances.
According to him, when there is significant internal wear, the correct solution involves mechanical repair.
Among the procedures mentioned are:
- Opening the engine
- Replacing worn parts
- Correcting internal measurements
- Proper dimensional adjustment
Commenting on the topic, Cleyton André summarized: “Oil does not fix failures.”
Correct oil use helps in engine preservation
The guidance presented by the specialist reinforces the importance of following the technical specifications determined by the car manufacturer.
Besides the correct viscosity, the engine design also considers chemical characteristics and additives present in the lubricant.
According to the consultant, altering these definitions without technical support can compromise the performance and durability of the mechanical assembly over time.
Therefore, the recommendation is to always maintain the officially indicated standard to avoid unnecessary risks to the engine’s operation.
Watch the full video
With information from Revista O Mecânico
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