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Does dark engine oil need changing before due time?


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Though engine oil has still over 40% life left as per last service kms, but I checked and it's quite dark and no longer in crisp golden color. Do I change oil before the recommended kms interval or should I wait safely for doing more?

Appreciate if someone can shed light on how to further diagnose engine oil usable condition and life than only based on kms criteria. Thanks.

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Hi kasim,

When you change oil, the new oil turns black almost immediately because not all of the old oil drains out of the engine. Some old oil sticks to the inside of the engine, and some remains behind in the oil pump, crankshaft, and other engine components. This old oil mixes with the new, turning it dark in colour.

This is not a problem, and it does not effect the new oil in meaningful ways. Oil turns black because it mixes with combustion products such as carbon and others, but the additives in the oil protect the metal parts of the engine against these combustion products.

Changing oil before it is due for a change is therefore just wasting money. Modern oil is designed to provide proper lubrication over the entire oil change interval time prescribed by the manufacturer of your car, so don't worry about the oil being black or dark in colour. This happens to all oil in all engines, and it is nothing to worry about.

However, there are a few things you can check about your oil. If the engine has overheated for instance, the oil will have a "burnt" smell. If it has this smell, the additives that protect against friction have  broken down because of the high heat. In this case, the oil does not provide enough lubrication, and you must change it.

Another thing to check is if the oil drips off the end of the dipstick. If it does, the oil is fine, and you don't have to worry. If it does not drip off, and a drop of oil hangs off the end of the dipstick when the engine is warm, the oil is too thick, and it must be changed. This usually happens when you have been topping off the oil level with different brands of oil, or if the crankcase ventilation system does not work properly. 

It is always a bad idea to mix different oil brands, because they are seldom compatible, which makes the oil thick and difficult to pump around the engine. The engine ventilation is controlled by valve that can become clogged, so have this checked out when you have your car serviced next time.

I hope this helps.

 

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I was just about to reply that apart from being dark you also need to check the viscosity of the oil and only change if its too thick, but MASTER taufiq has given some awesome insight on what is new learning for me as well. Love this, very educating man.

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