What Causes Dirty Oil?

Do You Need to Be Concerned?

One of the most common maintenance tasks that all vehicle owners perform is an oil change. It’s because of this service that you’re able to replace the old, dirty oil in your engine with new oil that’ll help improve your engine's performance and keep it clean. But, have you ever wondered what causes the oil to get dirty? What’s in the oil that gets it dark and gritty? Despite its nasty appearance, it may not be as negative as you think! Here are three common reasons why your motor oil has gotten dark and gritty over time!


This will typically be the case for your motor oil changing colors, and you shouldn’t worry! When your motor oil takes on this color, it indicates that it's simply doing its job! Since it’s responsible for lubricating your engine and keeping it clean, your oil is constantly cycled throughout the engine. Through each cycle, it will pick up some contaminants and slowly change colors. Although this color isn’t initially bad, it is important to replace the old motor oil with new oil as soon as you notice it!

Old Oil Filter

The oil filter is responsible for picking up the contaminants that your motor oil will pick up when it is cycling through your engine. When clean, the filter does a great job with keeping the oil clean and it’ll filter out most of the contaminants. The older the filter gets, the dirtier it becomes and eventually, it will lose its usefulness. That’s when the motor oil gets affected, as the filter can no longer collect the contaminants from the oil.

Black Goo

If you notice your oil has become dark and gritty and you don’t change it over time, eventually that oil will transform into a black goo that “globs” on the dipstick. This is always caused when you wait too long in between oil changes and it can cause severe damage to your vehicle’s engine. Some of that goo may end up trapped in your engine, so make sure you visit one of our technicians as soon as possible!

Written by Auto Stop