Taking the Mystery out of Engine Oil

A guide to all it does, and how it does it. The more we know about engine oils, the more wisely we can choose the best oil for our cars and MUV/SUVs.

Engine oils do more than you think. It’s easy to name the main function of engine oil: to lubricate every moving part of your engine with a protective film that reduces friction. But engine oil has at least four other duties, and failure to perform them all can seriously reduce the performance and life of your engine.

First, your engine oil cleans your engine. Gasoline and diesel engines can produce soot, ash, acids, and moisture that eventually form sludge, varnish, and resins. If they collect on critical engine parts, it means serious trouble. A quality engine oil keeps them suspended until filtered out or drained away when you change your oil.

Next, oil seals microscopic hills and valleys on piston rings and cylinder walls. Without proper sealing action, you’ll lose power and waste fuel.

Further, engine oil also protects your engine against rust and corrosion.

And finally, oil cools vital parts such as camshaft, rods, and pistons that the engine coolant in your radiator cannot reach. As much as 40% of the cooling job in your engine is performed by the oil in your crankcase.

Some facts about viscosity index

The Viscosity Index or ‘VI’ measures the change of an oil’s viscosity over a wide range of temperatures. The higher the VI of an oil, the less it will thicken when cold, and the less it will thin out when hot. A high VI oil will be more effective when lubricating your engine over a wide temperature range. Changes in viscosity and VI result in different viscosity grades, so you can pick the best grade for your vehicle.

Here’s a description of the five most common ‘SAE’ multi-grade oils:

0W-30: Premium winter grade oil. Provides year-round protection and fuel economy. Can be used where SAE 5W-30 is recommended.

5W-30: Premium multi-grade oil for easier cold-weather starts, maximum protection, excellent fuel economy and added engine life. The preferred grade for most cars built after 1989.

10W-30: The most commonly recommended multi-grade oil by OEMs in India. Delivers excellent all-round performance for the average driver.

10W-40: A premium multi-grade oil for hotter-than-normal running conditions, say where ambient temperatures exceed 40°C. It’s capable of providing extended engine life under such high temperature conditions.

20W-50: Thicker premium multi-grade oil for added protection against metal-to-metal contact; specially formulated to meet the needs of high performance Engines.

Making a change for the better

Today’s engines are efficient and sophisticated machines, often using multiple camshafts, turbo-chargers and other features. They also run faster and hotter, placing tremendous demands on engine oil performance.
That’s why it is essential to follow a strict oil-and-filter change schedule for your car. Changing the oil and filter remove harmful contaminants that may build up in your oil.

A fresh supply of engine oil with its specially selected additives will restore the protection your engine needs against corrosion, gum deposits, excessive wear, and other problems.

The oil and filter should be changed at the interval recommended in your owner’s manual. Every 5000 -10,000 km or 6-12 months is a common recommendation in India, especially for the BS-III Engines.

Speaking of performance additives

Most oils look, feel, and smell the same but their performance can be vastly different, thanks in part to their ‘in-built’ additives. Additives suspend dirt, inhibit foam, improve cold-weather flow, prevent corrosion, reduce friction, and add other qualities.

Many specialty additives or oil treatments are sold separately as brand names and promise longer life or extra performance for your engine. Remember that modern oils are recipes with measured portions of ingredients. Upsetting the recipe balance could lead to problems.

An oil formula may include a little anti-wear additive the same way a cake includes a pinch of salt to bring out flavour. If a little salt works, should you add more? Probably not, and the same goes for oil additives.

Believe in choosing the best quality oil you can afford and change it according to your Owners’ Manual is wiser in the long run.