Why Change Car Oil? 101-What You Need To Know

Why Change Car Oil? 101-What You Need To Know

Car Oil Why Change It ?

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Car oil deteriorates as soon as you turn the key to start the car, burnt fuel residue contaminates the engine oil as you drive, so why change car oil?

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This question needs breaking down,

  • What is the purpose of having car oil in your engine?
  • How does it deteriorate?
  • How regularly must Car Oil be changed?

The purpose of oil in your car’s engine.

All moving parts in a car engine should not touch or have very little contact with each other to eradicate or reduce friction, causing heat, therefore a car engine is designed with very small microscopic clearances measured in 1000th of a mm, and oil is needed to fill these clearances, the typical oil clearance on our modern cars are between 0.025mm and 0.089mm.

This is the clearance between two interacting parts, so oil is put into this clearance to prevent the two interacting parts from touching, allowing movement without the 2 parts binding due to heat caused by friction.

Small oil clearances
Oil Clearances Are Minuet


Oil Clearances
Crank Floating On A Layer Of Oil

Looking at a drop of oil under a microscope one can see many little round molecules bound together enabling constant movement, therefore ideal to use as a lubricant between moving metal surfaces.

The only disadvantage is that it deteriorates due to the various factors mentioned below and has to be changed periodically.

Engine Oil is like the Blood in the Human Body when Contaminated, it causes Illness.

Microscope View Of A Drop Of Oil
Engine oil particles as seen under a Microscope

The Deterioration of Engine Oil 

Engine oil deteriorates due to Moisture, Unburnt Fuels and Acids contaminating the Engine Oil while the engine is operational, making it appear black and thickened over time.

With modern vehicles, that use Fuel Injection Systems, less build-up of Fuel Dilution and Harmful By-Products in the Engine Oil occurs as opposed to the Older Cars, using Carburettors, therefore the Modern Car’s Service Intervals are extended.

Recommended Oil Change Intervals

Older Carburettor Cars – 6000 km to 10000 km or 8 months, whichever occurs 1st – Mostly Mineral and Semi-Synthetic Oils used.

Modern Fuel Injection Cars – 15000 km to 25000 km or 1 Year, whichever occurs 1st – Semi and Full Synthetic Oils used.

Synthetic Car Oils, though more expensive than Mineral Oils, have more advantages, such as a more consistent lubricating quality,  due to the much lower levels of Sulphur and more Synthetic Additives contained within, and can be used in the engine for extended periods.

The Difference Between Mineral And Synthetic Oils
The Difference Between Mineral And Synthetic Oils

So, in a nutshell, these are the main reasons that engine oil should be changed as per the manufacturer’s recommended intervals, which are measured in mileage or time covered, whichever occurs 1st.

Cars driving longer distances at a time incur less oil contamination, due to the evaporation of contaminants, as opposed to a car that drives shorter distances at a time, as they seldom reach peak operating temperatures.

Note:- Diesel powered car’s service intervals (6000 Kms to 10000 Kms or 6 months, whichever occurs 1st), are much shorter than petrol-powered cars, due to the High Sulphur content in the Diesel Fuels, contaminating the Engine Oils, thereby deteriorating the Engine Oil at a much faster rate.

Note:–  It is vital to change the Engine Oil Filter at each Oil change as the Oil Filter traps most of the contaminants to prevent even more rapid oil deterioration.

I strongly recommend an Engine Flush at each regular service interval, as it helps to break down carbon build-up and removes sludge inside the engine, it also restores engine cleanliness in preparation for the new engine oil.

What Is The Best Car Oil For Your Car?

Oil on dipstick
Clean Oil

Consequences of Infrequent Oil Changes:-

  • Rapid Engine Wear
  • Noisy Engine
  • Loss of Power
  • High Oil Consumption
  • Higher Fuel Consumption
  • Engine failure

If it is the only Maintenance you Perform on your Car Annually, let it be the

Engine Oil & Filter Change, Including a Flush.

What are your views on changing Car Engine Oils? Comment below

Until Next Time “Safe Motoring”

gary de la cruz

Gary De La Cruz

I have been 30+ years in the motor industry, still hands on, and have great passion for my chosen profession, I learn new things each day and believe that "if you enjoy your work, you never have to work a day in your life"I believe in honesty, integrity and helping where help is needed.

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