no won't happen, unless you don't change the engine oil to the point it has broken down to sludge. Technically, there's no way in clogging up the oil sump as it just serve as a tank.

But sludge can indeed clog up lubrication channels within the engine.

Concur

Only the front number indicates the lubricating properties during cold condition. In the above case, both oils are rated 5w, so the cold start performance are similar during cold.

For it to matter when w40 makes a real difference compared to w30, the engine has likely been modified to face with really high component contact pressures and RPM loads.

For normal run of the mill stock car (mildly modified included), if the manual states can use xw30 or thinner, it means it will work with that viscosity rating. Spirited daily driving hardly stresses the oil to the point that was faced during lab test conditions to derive the specification.

As a matter of fact, pumping RON97 has more direct impact towards engine oil health as the higher sulfur levels in RON95 will eat into the acidity regulating additives at a faster rate. If the oil has gone "sour", the sulfur will react with the water content in the air and within the oil itself, creating sulfuric acid which really eats into the metallic components.

It will still remain w40 unless there's high levels of fuel dilution....what kind of oil is this that can't remain temperature stable? I guess a more appropriate comparative statement to what you're saying should be "....behaving like w30 at 25C"

Just so you know, i made that temperature level up, i don't know that exact science, but just a more appropriate clarification.

Even if you track your car in stock form, provided that you maintained the car reasonably, unlikely it will not overheat the engine oil. The faster you go, the cooling circuitry also works harder correspondingly. The added velocity of air also draws more heat away from the radiator and other heat sources.

It is very hard for people to accept that, unless track ALL the time or the car was purpose built for tracking/racing, if thinner oil that is within the stated spec in the manual, there would not have any noticeable ill effects (even if you track once in a while in stock form).

If you really want first hand experience, please spend some time looking through the pinned dedicated engine oil thread, very informative with used oil analysis to back up.

Also, please read have some readings valvetrain/drivetrain components and oil related articles in the "tech centre" segment of enginebuildermag website. It is quite deep for starters, but you get solid knowledge from real engine builders :
https://www.enginebuildermag.com/tech-center/

This post has been edited by wkc5657: Mar 11 2019, 04:29 PM

That is why manufacturers give a range instead of giving just 1 specific viscosity.

The engines are quite over engineered in some sense as no single driver's driving conditions and habits are exactly the same. And to cater for international markets with the same engine engineering, it has been built robust for quite a large range between 2 extremes (especially japanese car engines).

Here's the deal to all that still want to stand on viscosity is the main considering factor for engine protection. The real take is changing the oil more frequently can better protect engine internals. This situation will never allow too much contaminants to build up.


This post has been edited by wkc5657: Mar 13 2019, 11:23 AM

This makes it unique mah...

Malaysia truly Asia...try beating that

HX8 is one tier below helix ultra series, so priced cheaper