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Is “thinner” oil worse? Contrary to popular belief, modern low-viscosity oils are not only safe but often more effective in today’s engines. TotalEnergies Marketing Polska explains why it is essential to adhere to manufacturers’ recommended viscosity grades and warns of the risks of arbitrary changes.
Thicker oil doesn’t mean better protection
A persistent myth online claims that switching to a “thicker” oil will quiet an engine and reduce oil consumption. While some enthusiasts report such effects anecdotally, TotalEnergies experts in Poland caution that using the wrong viscosity can accelerate wear and even cause serious engine damage. Experimentation on your own vehicle is not prohibited, but deviating from the recommended oil grade carries significant risks.
Density vs. viscosity: understanding the difference
In everyday language, “density” is often confused with viscosity; technically, however, they are completely different parameters.
- Density refers to a fluid’s mass per unit volume.
- Viscosity measures a fluid’s resistance to flow.
Many drivers confuse these terms, assuming that low-viscosity oil “feels like water” at room temperature. In reality, however, engines operate across a wide temperature range, and modern lubricants are formulated to protect bearings, pistons, and turbochargers alike, both during start-up and when under high load.
More than just viscosity: the importance of oil formulation
Contemporary low-viscosity oils (e.g., 0W-20, 0W-30) result from close collaboration between engine and oil manufacturers. TotalEnergies formulates its products to meet stringent original equipment manufacturer (OEM) approvals, covering not only viscosity grade, but also additive packages and overall performance.
An OEM approved lubricant guarantees that the entire formulation, including the base oil and additives, matches the engine’s requirements. Using an unapproved oil, even one with the same viscosity, can invalidate these approvals and lead to mechanical failures.
Risks of arbitrary viscosity changes
At high operating temperatures, “thicker” oils may provide inferior cooling. This can raise temperatures around piston rings and turbocharger bearings, causing local overheating and potentially resulting in cracks or seizure of engine components.
They can also:
- Disrupt hydraulic valve-lifter operation.
- Impair belt-tensioner or timing-chain performance.
- Alter variable-valve-timing hydraulics.
- Hinder heat dissipation from engine parts.
Dangers of using an incorrect oil specification
Using an oil with the wrong viscosity or without OEM approval can additionally:
- Accelerate timing-chain wear due to poor soot dispersion.
- Dissolve sections of wet timing belts, clog oil passages, or cause belt cracking.
- Increase the risk of low-speed pre-ignition (LSPI) in direct-injection turbocharged gasoline engines.
- Promote sludge and deposit formation.
- Degrade diesel-particulate filters prematurely.
- Cause ring seizure and other catastrophic failures.
To ensure reliability and longevity, modern engines require precisely engineered lubricants.
When is a viscosity change permissible?
Manufacturers sometimes specify multiple approved viscosity grades (e.g., 0W-30, 5W-30, 5W-40), as well as operating-temperature ranges and required OEM approvals. If your owner’s manual lists alternative grades and you only use oils bearing the corresponding approvals, —you may safely switch. Otherwise, using a different viscosity without authorization can result in serious and potentially irreversible engine damage, even if the effects are not immediately apparent.