The Dangers of Choosing Oil That Is Too Thick: It Seems Smooth but is Silently Damaging the Engine

Many motorcycle users, especially those from earlier generations, often believe that choosing a thicker oil will help the engine run more smoothly, like a thick cushion protecting the machine parts. Is this a sound experience or one of the most harmful misconceptions?

In reality, that smooth feeling can indicate that the engine is bearing an invisible burden. Choosing oil that is too thick not only causes the bike to lag more but also silently leads to three serious losses in lubrication efficiency during startup, cooling effectiveness, and the engine's cleaning capability. This article will delve into the physics of lubricants, explaining why thicker is not always better and helping you choose the right type of oil to optimize the true performance of your vehicle.

1. Decoding the smooth feeling - A misconception about lubrication physics

Before analyzing the damage, we need to understand why choosing a thicker oil creates the sensation of a smoother-running engine, and why this is merely an illusion.

1.1. Hydrodynamic oil film: Thick is not always good

The goal of lubrication is to create a film of oil just thick enough to separate the metal surfaces and reduce friction. The smooth feeling when using thicker oil is actually because the thick oil absorbs and dampens the high-frequency sounds of the engine. It's like blocking your ears; the engine is still struggling, but you can't hear it clearly. That's the sound of sluggishness being muffled, not of better protection.

1.2. Oil pump: The silent struggle of the engine

Imagine trying to suck filtered water versus honey through the same straw. The oil pump in a motorcycle functions in much the same way. It is designed to operate efficiently with a specific viscosity. When you choose oil that is too thick, the pump has to work significantly harder to push the oil through all the nooks and crannies of the engine. This not only reduces the efficiency of oil circulation but can also prematurely wear out the oil pump itself.

2. Three invisible losses when choosing oil that is too thick

These are the serious consequences that many people often overlook, leading to rapid deterioration of the engine.

2.1. Loss 1: Engine dryness at startup - Lack of lubrication in the first few seconds

When a bike sits overnight, most of the oil flows back to the sump. At startup, the oil pump needs to push oil to distant parts (like the camshaft) as quickly as possible.

• Consequence: Thick oil moves very slowly in the cold. Studies on engine wear have shown that most wear occurs during the cold startup phase, before the oil flow can reach