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6 Vehicle Fluids You Need to Monitor

Some vehicle maintenance is obvious. You change your tires depending on the season and keep them rotated to get the best wear out of them. But maintaining your vehicle’s fluids may not be as obvious – both in what purpose fluid serves and in knowing what needs to be monitored.  

In this blog, we’ll go through vehicle fluids you should keep up with, how they’re essential to your vehicle, and we’ll make some general recommendations about how often you should have your mechanic change or replace these fluids. 

Engine Oil

Oil is the single most influential component of engine health and durability. Most people know engine oil needs to be changed every so often. However, the rationale behind routine maintenance is something most drivers do not fully understand.  

Suspending Debris

Engine oil (or motor oil as it is often called) acts as a cushion to the moving parts of an engine. Oil surrounds contaminants such as road debris, isolating them from contact with engine parts. High quality oils have more ability to suspend particles than less expensive formulas. Oils are also formulated to perform at specific temperatures. In Fairbanks, lubricants often have to be changed out in new vehicles in order to work properly in our climate. 


Oil is slippery. This is what we most often associate with the purpose of engine oil–keeping things flowing smoothly. Slippery happens to be the best way to describe the function of engine oil lubrication. 

Viscosity is a measurement of “slipperyness”. Over time, the chemical bonds in engine oil break down. If you are familiar with “gluten structure” in bread baking, think of engine oil the same way. When bread is kneaded, the gluten properties of wheat flour become enmeshed forming a network of stretchy dough capable of trapping air. This is how you get a fluffy loaf of bread.

Similarly, oil has properties that allow it to stretch, seamlessly coating every interior surface of the engine. As oil wears, the bonds that give this fluid its stretch, break down. Worn oil becomes more sawdust than lubricant and engine parts abrade quickly. 

Oil Change

Manufacturers cite the optimum maintenance schedules for each vehicle depending on the viscosity and longevity of fluids they have paired with specific engines.  The standard recommendation for changing oil is every 3,000 to 5,000 miles. 

However, in Fairbanks these numbers have to be adjusted to allow for the amount of time engines idle. Engine idling does not appear on the odometer, so it cannot be tracked. Our recommendation is to change oil on a timed schedule, regardless of manufacturer. September/October, January, April/May. This schedule ensures optimum performance and longevity in our harsh environment. 


Coolant (also known as antifreeze) is a fluid designed to absorb heat. Engines are cast aluminum or other metals that have passageways built into them (think a maze of Roman viaducts). These pathways are pressurized and charged with circulating coolant. The cooling fluid absorbs excess engine heat and dissipates it by passing through a radiant cooling mesh.  

Coolant Flush

Similar to engine oil, the chemical properties that enhance cooling fluid break down with time and use. Coolant becomes thick and sludge-like, creating hot pockets in the engine system due to slow-moving fluid. Chemical decay also causes corrosive Ph balance conditions that eat away at metals, rubber, and other materials throughout the engine system.  

Coolant is designed to be flushed completely because it wears out. Coolant renewal is a serious maintenance consideration, like brakes or tires. 

Coolant Leaks

Because the cooling system is a complex, pressurized network of hoses and reservoirs, there are many intersections vulnerable to leakage. Often small leaks will result in low coolant or an under-pressurized system. Traditionally, drivers have added coolant or even water to the coolant reservoir in these instances. This is no longer a reliable practice for car owners. 

Coolant formulas are very specific and paired chemically with the materials used in engine builds. Straight water  is no longer compatible with most systems. 

Brake Fluid

Aside from brake pads, brake fluid is one of the most important parts of hydraulic braking systems. It helps increase the force of the brake pedal and turns that force into pressure on the brake pads or shoes. The harder the brake pedal is pressed, the more pressurized the brake fluid becomes which  increases the stopping force applied to the brakes. 

Brake Fluid is hydroscopic, meaning it attracts water from humidity in the air. This moisture combines with hydraulic fluid creating a slurry that absorbs pressure rather than transfers it to the braking mechanisms at the wheel. Technicians assess brake fluid health by measuring the amount of moisture or corrosion present. If fluids fail this test, they must be flushed completely and replaced. 

Generally, brake fluid flushes are recommended every 30,000 miles or approximately every two years. If you live in a place with a lot of salt or corrosion, this can compromise brake hose linings which makes hydraulic fluid more susceptible to moisture. 

Transmission Fluid

Transmission fluid is absolutely essential for the operation and performance of vehicle drivetrains. Like engine oil, transmission fluid helps lubricate the moving parts inside the transmission case. Transmission fluid also acts as a cooling bath for these sensitive parts.

Most vehicle manufacturers recommend changing transmission fluid every 60,000 to 100,000 miles, but this mileage is entirely vehicle dependent. 

Continuously Variable Transmissions (CVT) are a good example of climate-specific maintenance demands. Although most manufacturers recommend 30,000 mile fluid exchanges, in harsh northern climates that number is reduced to 15,000 at the most. If fluids go more than 15,000 CVT transmissions will fail.  

Power Steering Fluid

Power steering is the most dynamic hydraulic system in vehicles today. Pressures in hoses and fittings are highest in the power steering system. This intense pressure can cause holes to form in hoses at flex points and junctions between rubber and metal materials. Leaks in power steering cause the hydraulic pump to cavitate or starve. When a pump does not have enough fluid, it literally destroys itself due to over-heating. 

Most power steering system components will need replacing during the life of a vehicle. This makes flushing the system a by-product of repair rather than a scheduled maintenance activity. However, power steering is not something that can be ignored due to the probability of leaks. Regular inspections are critical to both performance and longevity in the steering system. 

In Alaska, wear-points in the power steering systems develop leaks more rapidly than in other climates. At Metropolitan Garage we recommend upgrading hoses to an arctic grade material that endures cold temperatures. 

Without upgrading these hoses, vehicles run the risk of losing steering altogether if a hose or other material in the system fails. 

Windshield Washer Fluid

Windshield washer fluid may be one of the simplest forms of vehicle fluids. In Alaska, windshield washer fluid may seem simple, but it is not! Wiper fluid, if not correctly calibrated to a cold temperature, will freeze and expand  throughout the plastic distribution system to the front and rear windows. There are many feet of small tubes that deliver fluid to spray nozzles in the system. When these freeze, they split, leaking fluid throughout the interior and exterior of the vehicle. 

If you have a leak or questions about any of your vehicle’s fluids and corresponding systems, schedule an appointment with our mechanics or call to talk to one of our experts.