The different mechanical systems in your vehicle need to have lubrication while they are operating. The engine, the engine's cooling system, the transmission, transfer case, differential(s), power steering, brake, and hydraulic clutch. Not every vehicle is equipped with all of these systems, but each of these systems need special fluid to operate. The fluid for these systems is designed to lubricate, clean, cool and condition during the operation of the system.
As the fluid deteriorates over time, by age and/or use, it breaks down and the properties within that fluid can no longer complete the job they are designed to do. When the fluid turns dark, discolored or brown it is because particulates that are cleaned out of the system it is operating in are suspended within the fluid. These particulates change the fluid color, can be abrasive and can sludge and collect within the system it is operating from and can actually cause damage over time. The fluids can also pick up contaminates from the environment like moisture, that can break down the fluid so it is no longer effectively lubricating, cleaning, cooling and conditioning the system that it is in.
Most of these fluids start out new with a translucent quality to them and are tinged at times by a color. For an example engine oil has an amber, transmission fluid is generally pink, brake fluid and power steering fluid are generally clear. The engine cooling system is generally the only one that is not translucent and depending on the vehicle you own could be a variety of colors, green, gold, pink, blue or clear are most common. Remember to never mix the coolant with a different type, only use what your vehicle is designed to be operated with for the best results. Mixing different types of coolant can at times cause a gel effect within the coolant and can cause issues within that system.
If it is being recommended to you that the different fluids in your vehicle are getting dark or discolored and you are unsure, ask for a sample of the fluid and an example of the color it should be. It is the best maintenance practice to keep those fluids clean so that they can do the job they are designed to do. We do not recommend waiting until they are super dirty or dark to have them replaced.
Most fluids do not need to be changed very often a general guide is listed below:
- Engine Oil: every 6 months or 3,000 to 5,000 miles
- Transmission Fluid: every 2 years or 30,000 miles
- Engine Coolant: every 2 years or 30,000 miles
- Power Steering/Brake/Clutch: every 4 years or 50,000 miles
- Transfer Case/Differentials: every 4 years or 50,000 miles
Listen and learn from your trusted repair facility and have them keep you informed as to the condition of the fluids in your vehicle. Then of course repair any leaks that occur in any system, because if one of the system runs low on fluid it can affect the operation and cause damage.