Effects of engine oil on fuel economy

  • Jun 26, 2014
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The type of engine oil can make a huge difference to the fuel economy of your car. Here's a guide to pick the right oil

Synthetic engine oil

There are several ways to improve fuel economy from driving with a light foot to over-inflating tyres but few would know that picking the right engine oil can make your car go that extra mile too. There are three kinds of oil you can purchase, mineral oil, semi-synthetic and fully synthetic. Mineral oil is the basic stuff just used to protect your engines and requires frequent changing. Semi-synthetic oils reduce engine wear, provide better protection in cold starts and oil change intervals go up compared to mineral oils. Fully synthetic oils enhance performance, have excellent cold starting ability and above all are more economical. 

Naturally then, the best choice of engine oil for better fuel economy is the fully synthetic kind. It all comes at a cost though. Synthetic oil is created in a lab by adding additives to the mineral oil in order to suit your specific needs of efficiency, performance and longevity. These additives add to the cost of the oil and so depending on your budget, choosing oil is a trade-off between price, efficiency and longevity. There are a few aspects you need to know before purchasing the right oil – 

Know your oil

Oil comes with different names and there are over a dozen different types to choose from. But every oil container has a rating on it which shows its characteristics. Take for example 5W30.  Oil is required in an engine at all temperatures from a cold start in winters to our sweltering summers. It doesn’t perform the same at all temperatures though. The W in the reading and the number before it is the winter rating and the second number is the rating when the oil is warm. Fully synthetic oils are designed to get a better winter rating. These oils are more efficient in cold conditions resulting in better fuel economy and lower engine wear. Depending on the climate you live in, the oil you choose will differ. Warmer places can use higher rating oil.


Oils can be termed as thick or thin. Thick means high viscosity oils and thin is low viscosity. Lately, you might have noticed manufacturers marketing more fuel efficient oils as part of their development for a new car. These are nothing but lower viscosity oils. Oils need to be thin when cold and thick when warm. To get the right mix, multigrade oils are your best bet. Multigrade oils have polymers added in the oil that are coiled up when cold and thus keep the oil thin. When the oil warms up, these polymers unwind to increase the viscosity of the oil. The viscosity of an oil can be understood by its viscosity index.


Know the time intervals between oil changes. These are manufacturer prescribed after testing the chosen oil’s effectiveness during testing. If you change oil, check its rating with the ones used by the manufacturer to the readings we have mentioned above and set oil change intervals accordingly. The sooner you change your oil, the better as the engine life increases and it performs at an optimum level to return better fuel economy.

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