Car owners may easily confuse differential oil with the transmission or gear oil, which are distinctive from one another. Over time the differential fluid breaks down and doesn’t protect the bearings and gears as it used to, which can lead to a quickly heated and prematurely worn-out differential.
Differential fluid has a translucent light golden color which may darken over time. So, this differential fluid color chart will assist you in understanding whether or not the differential fluid needs a change. It may also help to diagnose the problem and how serious the problem is in your car’s differential.
Differential Fluid Color Chart
Differential fluids may change their color for many reasons over a certain time period- if driven in water or on muddy terrain, you drive off-road often, or you tow a tractor on your truck. You may not notice any change in the differential fluid until there’s a leak on the ground, which is why you need to do occasional checkups.
| Fluid Color | Fluid Color & Condition | What The Color Indicates To |
| Golden yellow | Transparent Yellowish Golden Fluid Color | Regular differential oil color. |
| Green | Semi-Transparent Green Fluid Color | Uncommon, though, a type of differential fluid can be of translucent green color. |
| Light Olive Green Color | Opaque Light Olive Green Fluid Color | The milky or opaque fluid color indicates contaminated oil. |
| Gray | Gray Opaque Fluid Color | Dirty and contaminated fluid. |
| Black/Dark Brown | Dark brown/Black Color Fluid | The fluid is contaminated and possibly oxidized. |
You may notice one of the following color patches from a test check and what it indicates.
Golden yellow
The manual differential fluid color is generally golden or yellowish-golden. A few times, it can be different. If you notice the fluid color is yellowish or golden, but it has a little smell, then you don’t need to change it unless it has gone opaque/milky from its true translucent form.
Green
Sometimes the differential fluid can be translucent green or greenish in color. In this stage, the oil is see-through and not contaminated at all. So, you don’t need to change it yet.
Light Olive Green Color
The differential fluid can turn into a light pea soup greenish color. The fluid turns into a milky, opaque form. Any milky transformation of your differential fluid is not normal, even though it remains pretty similar to its original color. It can be caused by contamination, and you need to change the fluid as soon as you can.
Gray
The thick sludge-like gray or light brown differential fluid color indicates contaminated or oxidized fluid. The fluid may be contaminated with water or mud and needs a quick replacement. It may also happen due to rust or pitting of the surrounding parts. So, it needs a change after a few days of running.
Black/Dark Brown
A differential fluid color, brown or black, that smells pretty strong, mostly in the front end, may indicate a broken axle seal due to which the oil is leaking. The grease may appear on the housing coming through the steering knuckles, which can also damage the knuckles.
How Do You Check The Fluid In The Differentials?
Well, unless the fluid drips out of the container, you need to find out yourself whether it needs a replacement or not. So, to check on the differential fluid, you need a
Step 1: Open the fill plug of the differential compartment.
Step 2: Use your pinkie finger or the dipstick and try to reach the floor of the differential fluid compartment. Or, you can just simply bend your finger and try to reach the oil.
Step 3: After getting some sample of the oil, you can test the fluid quality by doing two things-
- To do the blotting paper test, you only need a piece of blotting paper (or a piece of paper towel will do if blotter’s not available), on which drop a few drops of differential fluid. After about 30 seconds, you can notice the changes.
The fluid will be in its original color and may spread a little on the paper if it’s in good condition. Otherwise, it may be darker in color and is sticky in nature when it’s gone bad. Therefore, you need to flush the oil out and do a fluid change and, in some cases, a filter change as well. - It’s a pretty basic smell test where you just try to smell and understand if the differential fluid has retained its original odor. If it has a burnt smell, it is due to overheating. But if the differential fluid’s black but not burnt, then the fuel is oxidized, and you need a replacement.
If the fluid looks original, even though it might have a slight smell, it is alright to keep it. But if it has changed the color into a gray, black, or whitish green with a strong smell, mostly common in the front differential fluid color, you need to replace it urgently.
Note: We advise you not to change the differential just prior to a long road trip.
Frequently Asked Questions (FAQs)
How do I know if my differential fluid needs to be changed?
The contaminated or oxidized differential fluid leaves out signs during the operations. You may notice any of the following changes- contaminated oil has metal particles in it, low oil level, your vehicle may have a humming noise, vibrations during a downhill drive, notice grinding sound when turning a corner, etc. These signs can also indicate problems with other engine parts. So, you need to check all the differentials’ fluids in your truck.
How long should differential fluid last?
How often you should change the differential fluid completely depends on where you drive your car often, your vehicle’s condition, fluid quality, and the manufacturer’s guideline in the owner’s manual. However, frequent off-road driving may require oil changes more often. Though differential fluid can last between 30,000 to 60,000 miles in a general scenario, you should check the manual for the proper service interval to maintain a healthy gap between each oil change.
What should rear differential fluid look like?
Differential fluid has a light yellowish-golden color when new. It’s almost similar to the engine oil in consistency. The only difference is it is thicker. Among the two types of differential oil, synthetic oil outperforms natural crude-based fluid.
What happens if you don’t replace differential fluid?
Delaying differential fluid change can lead to many problems. Without adequate fluid or having contaminated fluid in the differential, the differential may wear out way faster than usual. It can also overheat, causing unavoidable safety issues and ultimately leading to a failed differential which is expensive.
Summing Up Notes
Your vehicle doesn’t have a filter in the differential. So it cannot sift out the contaminants or metals in the fluid. Keeping an eye on the differential fluid color occasionally can prevent severe damage. This differential fluid color chart helps you find out which color your differential fluid is and what’s the reason behind it.
Therefore, we advise you to check on the differential if you notice some of the significant differences related to it in your vehicle system, as we stated above. It’s not super difficult to change the oil. You can DIY for the oil change and drip out the old oil completely from your vehicle’s drive-train, but if you prefer, you can take help from a technician.
You Can Also Read:
- Transmission Fluid Compatibility Chart Explained for All Vehicles
- Dexron VI Compatibility Chart: Breakdown of the Compatibility
- Can You Use Brake Cleaner As Starting Fluid? Read Before Ruining The Engine!
Sadeek Matt, “The Human Truckopedia”, has dealt with all types of trucks for 6 years with another 2 years of experience in the automobile industry. He is one of our key team members who solve truck-related problems for Vehicle Bro’s content team to come up with answers to readers’ queries.
He loves scuba diving apart from handling trucks and according to team members, he’s a guy with a great sense of humor who loves living life to the fullest.
