Why does oil look colorful

If, however, the rays reach your eye out of step, they will cancel each other out due to destructive interference. Each color of light has a different wavelength. Hence, a given disparity in the path length will cause constructive interference of certain colors, whereas other colors will not be observed because of destructive interference. Because the oil film gradually thins from its center to its periphery, different bands of the oil slick produce different colors.

Newsletter Get smart. Sign up for our email newsletter. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Discover World-Changing Science. The following answer comes from Dinesh O.

Milky, foamy, or cream-colored oil can be an indicator of a head gasket leak if your exhaust is producing white smoke, or your vehicle is leaking coolant. Simply looking right under your equipment or vehicle's oil cap should reveal if your equipment is suffering from milky or frothy oil.

Typically this happens if the oil is exposed to water after raining or the equipment is not used long enough for the water on the engine to evaporate and burn off. Thick, black, or very dark motor oil usually indicates that your oil has been exposed to dirt or dust contaminants that lead to a soot build-up. Direct injection gasoline engines produce soot over time that causes standard motor oil to turn black and thick.

Soot is a byproduct of incomplete combustion and since soot particles are less than one micron in size they typically do not cause much engine wear. The problem with soot happens when the soot particles begin to agglomerate into larger wear-causing contaminants.

This is where the black thick texture may come from. It is very common for people to assume that there is a correlation between the color of oil, and the need to change the oil.

This is not necessarily the case. Many of the changes and elements your oil is exposed to will change the color so there is no actual way to tell if your vehicle needs to be changed by just looking at it. These are the big color indicators to look out for in your oils and lubes. As you have learned there is no sure-fire way to know what is wrong with your oil by just looking, however, these are some indicators that it may be time to replace or look into what is wrong with your storage.

We hope very much that you have learned something new. If you're in need of automotive lubricants feel free to reach out to us! If you are new to the SC Fuels blog, then consider subscribing for more useful and interesting topics!