Colour of oil


#1

Why the oil in due course darkens? Recently changed oil, has merged - it was black :frowning: How often it is necessary to change the oil filter?

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#2

When you mop the floor, doesn’t the water darken and become discolored as you clean the floor? In a similar fashion, since modern oil formulations contain detergent ingredients, the oil removes contaminants from the engine and places them in suspension. The discoloration of the oil indicates that the detergents are doing their job, and the oil will become progressively darker as it ages and as it picks up more contaminants.

The oil filter catches particles that are too large to be held in suspension by the oil, and it traps them. The filter should be changed every time that you change your oil.


#3

dark oil does not mean that the oil can no longer do its job, it means that it is doing ists job. Each engine is different as to how long it takes for the oil to darken up so you have to build an experiecne curve with your engine. Go with what is in the owners manual for oil and filter changes and you will be fine. Filters can be changed every oil change or every other depending on what is in the manual.

For your info diesel oil (in a diesel engine) turns black almost as soon as it is put in, color is not an indicator of the lubricating properties of an oil


#4

dark oil does not mean that the oil can no longer do its job, it means that it is doing its job. Each engine is different as to how long it takes for the oil to darken up so you have to build an experiecne curve with your engine. Go with what is in the owners manual for oil and filter changes and you will be fine. Filters can be changed every oil change or every other depending on what is in the manual.

For your info diesel oil (in a diesel engine) turns black almost as soon as it is put in, color is not an indicator of the lubricating properties of an oil


#5

Take some motor oil and put in a pan and heat it up to 300+ degrees, it will start getting darker. Its the oil breaking down.

As your engine is running, oil is pumped through the engine where it absorbs heat. It returns to the pan and cools some before the next trip. When you shut the engine down, a thin film of oil is left coating all those hot engine parts. Since it isn’t being constantly flushed away by fresh oil, this film gets very very hot and it breaks down and turns black. This is only a small amount of oil is affected. When the engine is started again, fresh oil flushes this thin film of black oil away, but it of course mixes with the fresh oil, darkening it a little. This process repeats with every shutdown and startup, gradually darkening the oil until it need to be replaced.

Turning black is only the first stage of breakdown. Black oil, up to a point is still doing its job. The second stage is where it gets thick and forms sludge. at this point, it can restrict oil from getting to needed places in the engine and the engine can be damaged as a result. The third stage is when it “cokes”, that is it forms a hard gritty substance, this will really wear out an engine very quickly.

Change the oil filter when ever you change the oil.