Parts to Replace After Reaching the 100,000-Mile Mark

Various vehicle components will naturally wear down as your ride accumulates more mileage. While 100,000 miles might seem a lot, in some cases, this isn’t even halfway through your vehicle’s lifespan.

A properly maintained daily driver should have no issues running past this milestone. It’s important to stick to your manufacturer’s recommended service schedule and replace worn parts before they completely fail.

Parts to Check or Replace Clocking at 100,000 Miles

Your engine oil and oil filter, transmission fluid, coolant, brake fluid, spark plugs, and timing belt are some examples of key components and fluids to check around the 100,000-mile mark.

Note: Be aware that some of the items mentioned here require shorter service intervals, so make sure you use reliable information to determine the proper service interval.

Engine Oil and Oil Filter

Periodic engine oil and filter replacement is critical to ensuring the health of your engine both up to and beyond 100,000 miles.

The engine oil and oil filter need changing at 100,000 miles because they could have metal shavings and carbon deposits, leading to decreased effectiveness, as the oil’s viscosity isn’t up to par. Oil analysis kits are available online for sending an oil sample to have it analyzed, and 100,000 miles is a good interval.

Transmission Fluid

Old transmission fluid may contribute to issues like gear slipping and rough shifting. As such, it’s important to get a transmission fluid change once your manual or automatic transmission hits the 100,000-mile mark.

If you use your vehicle to pull heavy loads the transmission fluid needs to be changed more often, and the heavier the load, the more often the needed change. Note that maintenance schedules have normal and severe service tables that apply to oil and transmission change intervals as well as filters, etc.

Changing your vehicle’s transmission fluid can be complicated and require tools the average driver won’t have in their garage. In most cases, it’s best to hire a mechanic and leave the job to a professional.

Coolant

Engine coolant keeps your car cool and the engine working at optimal temperatures. Like the fluids mentioned above, the coolant is prone to degrading and breaking down after a while, which could lead to overheating and other temperature-related issues.

You can always turn to a professional for assistance or flush the coolant yourself. Do note that draining the coolant from your vehicle can be a complicated process, so going to an auto shop could save you more time.

Brake Fluid

Another thing you should check and replace is your vehicle’s brake fluid. Moisture absorbed through microscopic pores in the brake lines and the cylinder can cause the fluid to degrade over time, not to mention copper contamination in the fluid from the brake lines. As a result, old brake fluid may cause your brake pedal to feel soft and increase your braking distance.

While you can do it yourself, it may be better to leave the flushing to experts as they’ll have more experience with the process. Flushing should only cost you a little over $100.

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Pro Tip: There are dip strip kits available online to indicate copper contamination, and you can measure the voltage in the brake fluid with a multimeter (from ground to the fluid in the master cylinder). More than 0.30 volts indicates that the fluid has absorbed too much moisture.

Spark Plugs

The spark plugs provide the spark within the combustion chamber to ignite the fuel and start the vehicle. Spark plugs may need to be replaced as early as 30,000 miles.

Most spark plug intervals are 100,000 miles on newer cars. On old cars with points ignition, spark plugs were replaced every 12,000 miles, but that’s a long way in the past and no longer pertinent.

You can change the plugs yourself if you’re wrench smart. If not, hire it done at a reputable shop.

Timing Belt

The timing belt is the rubber belt that synchronizes the rotation of several components, including the camshaft, crankshaft, and valve timing and on many engines it drives the water pump.

A damaged belt can, on interference engines (not all engines are), cause engine damage due to the pistons and valves colliding if the belt fails and the camshaft stops turning while the crankshaft is still spinning.

Once you hit the 100,000-mile mark, it’s a good idea to check the belt and replace it. You can do it yourself or spend up to $2,500 at an auto shop to save yourself the trouble. Go ahead and get a kit that includes a water pump and all the pulleys if the water pump is timing belt-driven.

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Cooling Hoses

Cooling hoses are often made of rubber and are designed to withstand intense pressure and extreme temperatures. They can fail without warning and need to be checked by experienced hands and eyes at the 100k mark. You won’t need to replace them all at 100k. Just be mindful that hoses aren’t forever.

Battery

It’s also important to check your battery to ensure it can still hold a charge. A battery is like an electrical fuel tank. Over time, it loses cold cranking amps (CCA) to the point that it’s too weak to spin the starter.

One early warning is if your dashboard clock resets to 12:00 when you start the vehicle, although sometimes the battery will just fail without warning. Pay attention to the way the engine sounds when you’re spinning it. If it’s spinning slower than it should, have the battery checked.

Generally, a car battery needs replacement every three years, but you should also keep an eye on it once you hit certain mile thresholds.

Clean and check the battery case for signs of corrosion, bloating, and leaks. Once you notice any of them, bring your vehicle to an auto shop for proper maintenance, as battery acid is harmful to you and the car.

If there are no leaks and you just want to replace the battery, you can do it yourself. All you need are the proper tools and a replacement unit.

Tires

The last thing you should look at when you reach the 100,000-mile mark is your tires. Make sure they’re not balding and are still in working condition. Note, however, that most vehicles go through a set of tires every 30k to 50k miles anyway, so there’s that.

The least you can do is to rotate the tires to spread tire wear evenly. If they look damaged, have a mechanic take a look or replace the tires yourself.