Guide to car engine oils: Mineral oil vs Synthetic oil

What is the best engine oil for your car? Mineral oil or synthetic oil. Most enthusiasts will tell you that synthetic oil is far superior – it has better lubricating properties, better consistency and longer life. But it is also far more expensive.

The reason synthetic oils are expensive is that they are formulated in a laboratory using chemicals which may or may not be sourced from petroleum products. They have a better consistency, uniform composition and are more tolerant to high temperature changes, which is why all racing cars and Formula cars run only on synthetic oils.

Guide to car engine oils: Mineral oil vs Synthetic oil

Mineral oils, on the other hand are cheaper, as they are extracted from the earth along with other petroleum products. The issue with mineral oils is that they tend to lose their consistency faster and don’t have that long a life. They also can’t handle high performance applications very well, as they are not that tolerant of temperature changes.

And then there’s the third type – the semi-synthetic oils, which are essentially mineral oils, with a blend of synthetic oil. This kind of oil is more affordable, as it is not as expensive as pure synthetic oils.

So how do you go about choosing the right engine oil for your car?

Here are a few points to consider about the choice of oil:

–          Viscosity: This is a rating that the oil has. A 0W-40 oil means it is a very thin oil, and suitable for  low operating temperatures. Higher temperatures need higher viscosity. Which is why CNG cars will do well to run on 20W-50 oil, and preferably synthetic oil. Refer to your owner’s manual for the right grade of engine oil for your car.

–          Oil rating: This is the specification of the oil for that engine denoted by codes such as API CH-4, API SM. Always use oil that exceeds this base specification (you will find this in your owner’s manual as well).

–          Drain interval: The duration between oil changes. This needs to be followed precisely and with clockwork regularity for the life of the car.

–          Type of oil: The choice is yours. Synthetic oil or mineral oil. Ideally a synthetic is better.

–          Oil filter: Don’t forget to change your oil filter with each oil change

–          Oil flush: An engine oil flush is essentially a very thin oil that cleans out the gunk and grime from dirty engines. Not needed for new cars. Use a flush only if you have an older car, and if you are shifting from mineral oil to synthetic oil. Otherwise, this is not needed.

Advantages of synthetic oil

–          High performance and smooth running

–          Less impurities lead to longer life

–          Has high heat tolerance

–          Has better lubricating properties, due to smaller and uniform molecular structure

–          Longer intervals between oil changes

Disadvantage of synthetic oil

–          High cost (at least 5 times more expensive than mineral oils)

–          May not be suitable for older cars

–          Can prolong the running-in period of a car

Ideally, if you can afford it, use synthetic oil for your car. But do this only after the first 15,000 km or so, as the engine needs time to settle down and run-in properly, while synthetic oils can hamper this process, as its superior lubricating properties won’t let this happen quick enough. If your car comes with synthetic oil from the factory (like Volkswagen, Skoda cars), then you need not bother with an oil change till 15,000 km or 10,000 km depending on what the car manufacturer recommends.

What’s the ideal oil-change interval for synthetic oil?

If you are using synthetic oil, the ideal oil change interval is 15,000 km between changes. However, it also depends on the driving conditions. If you drive in extreme stop-go traffic and high temperature variation conditions, it is best to reduce the drain interval to 10,000 km, as this will help keep the engine cleaner.

What’s the ideal oil-change interval for mineral oil?

Mineral oils have a recommended drain interval of 10,000 km usually. But with tough traffic conditions, it is advisable to lower the change interval to 7,500 km or even down to 5,000 km in some instances. If you are cost conscious, it still makes sense to change every 5,000 km, as a mineral oil costs about 1/4th of what a litre of synthetic oil costs. For example, a litre of Mobil 1 synthetic oil (5W-40) costs Rs. 950, while a litre of Servo mineral oil (20w40) costs about Rs. 210.

Even if you are using a semi-synthetic oil (like Castrol GTX Magnatec), stick to the drain intervals for a mineral oil, as the synthetic part will only help with engine cleaning, while the mineral part of the oil anyway has a limited life span.

How to change your engine oil?

Take the car to a garage to get the oil changed, as it is much easier putting the car on a lift or on a ramp to change the oil. But if you are the adventurous kind who can do this at home, here are a few pointers.

You will need a pan that can hold at least 5-6 liters of oil (for the old oil), an oil filter removal tool (which is a C-shaped clamp), spanners, waste cloth, funnel and fresh oil and new oil filter.

Warm up the engine.

Park the car on level ground.

Lie under the car (if you can fit in) and identify the oil drain bolt on the bottom of the engine oil sump.

Loosen the drain bolt with a spanner, but before you remove it, place the pan under it to collect the old engine oil. Let the oil drain into the pan.

Next loosen the oil fliter with the oil-filter removal tool. Unscrew it completely and take it out.

Then open the oil filler cap on the engine and cover the opening with a cloth to prevent dust going in. Removing this cap will allow any residual oil to flow out into the pan. Also remove the oil dipstick.

Take the fresh oil filter and coat the rim of the filter with some fresh oil before you screw it in.

Then replace the oil drain bolt and tighten it properly, taking care not to overtighten it as it can get damaged and also ensuring that any washer with it is still intact.

Put a funnel over the engine oil filler cap and pour in the fresh oil slowly and patiently. Make sure you put in only the recommended quantity as indicated in your owner’s manual.

After you have filled oil, check the level using the dipstick. Usually it will be a little lower than usual, but this should settle down once you start the engine and run it for a bit.


Do share any other oil change tips that you have for your car. Happy driving.

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