Why Old Vehicles Should Use Thicker Oil? Unraveling the Mechanism for Compensating Engine Wear

Everyone advises that older vehicles should switch to thicker oil. But do you really understand why this is the case and the mechanism behind this recommendation? The answer is not simply because the engine is worn. It lies deep within the physical laws of pressure, sealing, and hydrodynamic oil films. This article will explain why the advice for older vehicles to use thicker oil is backed by solid scientific foundations.

We will take a closer look inside an aging engine, pinpoint exactly which components are worn, and explain scientifically why the recommendation for older vehicles to use thicker oil is an effective compensatory measure that helps extend your vehicle's lifespan.

1. The case study of an old motorcycle engine: Which components are actually worn?

To truly understand why older vehicles should use thicker oil, it is essential to recognize that the engine is subjected to wear in multiple areas simultaneously, leading to unpleasant symptoms.

1.1. Piston and Cylinder Clearance: The battle against gas leakage and oil consumption

After millions of up-and-down cycles, piston rings lose their elasticity, and the cylinder walls acquire micro-scratches. Respected studies from the Society of Automotive Engineers (SAE) have clarified an important fact: the primary cause of oil consumption stems from the loss of perfect sealing between the trio of piston - rings - cylinder wall.

• Consequences: Reduced compression pressure (gas leakage): Compressed gas in the combustion chamber leaks down into the crankcase, causing the vehicle to lose power and responsiveness.
• Oil consumption: Oil from the crankcase leaks into the combustion chamber and is burned. This is the main cause of motorcycles emitting white, blue, or black smoke and experiencing abnormal oil loss. If you're interested in learning more, you can explore the causes and solutions for rapid oil consumption in motorcycles. This situation is the primary and most common reason for the recommendation that older vehicles should use thicker oil.

1.2. Bearing Caps on the Crankshaft and Connecting Rods: When gaps cause oil pressure loss

The soft metal bearing caps between high-speed moving parts like the connecting rods and crankshaft will wear down, creating larger gaps than the design standards.

1.3. Valve Seals and Valves: The silent pathway for oil leaks from the cylinder head

Rubber seals enclosing the valve stems become hardened over time due to heat, losing their ability to fit snugly.

• Consequences: Oil from the cylinder head will leak along the valve stems into the combustion chamber, which is another cause of oil consumption and the accumulation of carbon deposits in the combustion chamber. This is a reinforcing factor that