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Maintaining Your Car at 100,000 Miles: Key Items to Replace at This Maintenance Interval

Chris loves automobiles and has maintained, repaired, and/or restored over a dozen of them in the last 15 years.

100k Miles Maintenance Checklist

These days, people are keeping their cars longer than ever before. In fact, according to the latest statistics from R.L. Polk Co, the average car on the road is now almost 11 years old. There are several reasons for this striking statistic. However, the most obvious reason is the fact that the economy took a nose dive in late 2008. So if you are like the millions of people electing to drive their cars beyond the 100,000-mile mark, it would be wise of you to invest the money into getting the proper maintenance needed at this integral moment in your car's life.

Before diving into the biggest maintenance project of your vehicle's life, be sure to consult with the maintenance schedule for your vehicle. Since every vehicle is different, many items may or may not apply to your particular car or truck. If you have lost or manual or are otherwise in doubt, don't be afraid to read on or ask your local reputable auto shop for advice. In addition, most auto manufacturers have made copies of the owner's manual available online.

Below is a general guide to what a typical car may need maintained at the 100,000-mile mark.


Fluids are the lifeblood of your vehicle. Over time, dirt and debris can begin to clog and overwhelm your engine, and its parts eventually leading to an expensive repair. In addition to this, many fluids have additives that lose their effectiveness over time. So it makes sense that replacing them with new and clean liquids will help to ensure that you can drive your car for another 100,000 miles.

For most cars, it is recommended that you completely replace:

  • Oil
  • Transmission fluid
  • Coolant
  • Power steering fluid
  • Brake fluid

In some cases, certain fluids will reside in a permanently sealed reservoir for which replacement is not necessary or possible.


Your vehicle's serpentine belts are made of a special kind of rubber designed to work within a hot engine compartment. However, this does not mean that they will last forever. When inspecting the belts look for signs of:

  • Cracking
  • Missing ribbing
  • Marring
  • Striping
  • General brittleness
  • Uneven wear

If you see any of these signs it means that it is time to replace them with a fresh belt. If your belt is wearing unevenly it may mean that a pulley or belt tensioner also needs to be replaced.

The mighty wrench, a mechanic's best friend.

The mighty wrench, a mechanic's best friend.

Timing Belt and Water Pump

Besides changing your oil, this maintenance task is probably one of the most important items that you can do at 100,000 miles because the damage caused by a broken timing belt on interference engines can be extremely costly to fix. Statistically speaking, there is a really good chance that your timing belt will eventually break. This is especially the case if you regularly drive in really hot or really cold climates or where driving conditions are especially harsh.

Even though this maintenance item is costly (both time wise and money wise), do not put off getting your timing belt replaced. And since you will be going to all of the trouble to have this replaced, you might as well have the mechanic replace the water pump too. In some cars, a new timing belt tensioner will also be required as part of this maintenance item.

Tires and Brakes

Since your vehicle's tires are the only thing that actually touches the pavement, it is vitally important to ensure that they are in good working order. Check the tire's inflation level as well as tread depth. Inspect them for signs of uneven wear, cracking, and bulging. Don't forget to rotate them either. If the tires have uneven wear, or the vehicle is pulling to one side, it may be time for an alignment too.

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When replacing tires it's always best to replace all four of them at the same time. If you can't afford four tires, it is okay to purchase two instead (either the front pair or rear pair). Furthermore, it is vitally important to choose high-quality tires designed for the environment that you drive in on your particular vehicle. Good tires will result in improved handling, acceleration, and braking while also optimizing fuel consumption.

Along with tires, your brakes are another vitally important piece of equipment that requires maintenance. Check your pads and/or shoes to make sure that there is plenty of material left to keep you stopping in the future. If you have disc brakes, inspect the rotors for signs of uneven wear, pitting, or warping. If you see any of those items, it might be a good idea to have them turned.

If you have to have your rotors turned or replaced, you should also go ahead and replace the brake pads as well. Be sure to invest in high-quality brake pads as they will last significantly longer than cheap ones. In addition, high-quality pads (or shoes for that matter) will also help you stop your vehicle more quickly than cheap ones.

Rust can destroy a vehicle over time.  Check your car for rust and take care of it as soon as you can.

Rust can destroy a vehicle over time. Check your car for rust and take care of it as soon as you can.

Other Things to Inspect or Replace

In addition to belts and fluids, most auto manufacturers recommend replacing a few other items as well. For instance, changing out your spark plugs is a relatively easy task that should be part of the 100,000-mile maintenance. Don't be afraid to change the car's fuel filter, air filter, internal air filter, and PCV valve too. If your car is particularly old, it is probably time to replace the cap and rotor located on the distributor as well.

While you are under your car changing the oil, you should inspect the undercarriage for signs of rust and other damage. If there are signs of rust, hopefully you caught it early enough to get it taken care of properly. Another thing that you should do is to go ahead a lubricate all of the moving joints and hinges on your car. This includes things like the door and seat hinges.

And finally, it is a good idea to inspect all of the rubber hoses located under your hood. This includes the coolant and oil lines as well as vacuum hoses and fuel lines.

How Much Does the 100,000-Mile Maintenance Cost?

Since the 100,000-mile maintenance is the largest and most in-depth of all of the maintenance intervals, it is also the most expensive. Still though, paying for maintenance will save you a lot of money and headaches in the long run. If you have an interference engine, did you know that repairing one damaged by a broken timing belt could cost you upwards of $3,000 to repair? I have even heard of one case where the repair bill was over $5,000! Given that proposition, getting the maintenance will sound like a good deal.

The chart below outlines the typical costs of many of the items that typically need to be maintained at the 100,000-mile mark.

Cost Comparison of Doing Your Own Maintenance vs. Going to a Mechanic

These are the usual cost ranges for each service and may differ depending on where you live and what products are used.

DIY CostMechanic Cost

Oil Change



Coolant Flush



Transmission Fluid



Brake Fluid



Power Steering Fluid



Serpentine Belts



Timing Belt & Water Pump



Brake Pads/Shoes



Replace/Turn Brake Rotors



Fuel Filter (Outside of Gas Tank)



Air Filter



PCV Valve



Spark Plugs




$0 (if you have the tools)


Lubricate Chassis, etc



This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

Question: I am sitting at a Honda dealership waiting for an oil change. My 2015 Accord coupe 4 cylinder just hit 109k. They suggest a $1500 100k service. I do have an independent mechanic. Would his price be substantially less? Or do you recommend staying with the dealer?

Answer: Dealships generally charge a lot more than local mechanic shops. They also tend to use OEM parts and offer longer warranties on the parts and labor than a local mechanic would. However, your local mechanic may be cheaper but might also use remanufactured or lower-end parts. Remanufactured and lower-end parts aren't necessarily a bad thing. Personally, I do most repairs and maintenance myself. However, in some cases I have used a local shop for "big" jobs or for things that require specialized tools or equipment. If you have a local mechanic that you know and trust, I would recommend going with them. I would expect his price to be lower than the dealership for the 100k service. If you're concerned about the parts they may use, you can always ask or request they use OEM parts.

Question: My 2012 Honda Civic has just turned over at 100k. Should I be looking at changing the spark plugs or, does this vehicle have igniters? Also, will I need a valve adjustment or drive belt replacement?

Answer: Most likely, the spark plugs need to be changed. The interval for changing spark plugs varies from every 30k miles to every 100k miles depending on many factors such as driving conditions, gasoline quality, and especially the type/quality of spark plugs that are in the vehicle. A valve adjustment is also likely needed as well if it has not been done previously. Drive belts may or may not need to be replaced depending on their condition. When my Honda Civic hit 100k miles, I changed the timing belt, water pump, serpentine belts, spark plugs, and adjusted the valves. This was 80,000 miles ago and I haven’t had any problems with the car since.

Question: I have a 2012 Honda Civic with 100,000 miles, and this year of Civic has a timing chain. Does this amount of miles on a car affect the water pump? What is the difference between serpentine and drive?

Answer: If your vehicle has a timing chain then it is not likely that it will need to be changed. Timing chains can stretch and loosen over time, but for the most part they are designed to last for the life of the engine. On the other hand, a water pump can fail at any time. It is normally recommended to replace the water pump when the timing belt is changed because the procedures are essentially the same and there's a significant cost savings when replacing both at the same time. However, since the timing chain would not need to be replaced then the water pump should not be replaced unless there is a problem. The water pump is not a normal maintenance item that needs regular replacement, however I would check your vehicle's owner’s manual to be sure on what needs to be replaced when.

The serpentine belts are the ones that drive the other components in the engine such as the power steering pump, air conditioner, and the alternator. These belts should be visible from the engine compartment.

Question: Should the engine mounts be replaced at a 100,000 maintenance?

Answer: The engine mounts in most vehicles do not have to be replaced at regular intervals. In the right conditions, many engine mounts can last for the life of the car itself. In very hot or very cold climates or in harsh driving conditions they may not last very long.

However, engine mounts should be inspected frequently and checked for major cracks or broken rubber. Use a flashlight and a small mirror if necessary to inspect all around the rubber mount. Symptoms of a broken engine mount include excessive engine vibration and a shifting or clunking of the engine itself when accelerating or braking. If you suspect that you have a broken engine mount it's important to replace it as soon as possible. In many cases it can be relatively easy to replace on your own.

Question: What does it mean when lights are dim on the dashboard?

Answer: This usually means that there is low voltage in the battery. Either the battery is failing to hold a charge, or the car's alternator is not charging the battery correctly. I would recommend getting your battery tested to determine what the cause of the problem is. Also, if your battery is more than three to five years old, it may just simply need to be replaced.

Question: Should I check universal joints in my vehicle at 100,000 miles?

Answer: Universal joints are used on most 4-wheel and rear wheel drive cars to transfer drive power from the transmission through the driveshaft to the differential. Primarily, U-joints should be inspected frequently, not just at the 100,000 mile mark. The main component of maintaining universal joints is to make sure that they are well lubricated and are functioning properly. However, a good number of u-joint assemblies are factory sealed and thus cannot be lubricated. If they are damaged or worn then it may be necessary to replace them.

Inspection of the U-joint should include checking for leaking lubricant, rust, or excess wear or play which could manifest itself in a number of ways. This includes: 1) Squeaking that can be heard from under the car, usually when traveling less than 5mph, 2) A clunking noise that occurs when accelerating from a stop, or 3) High-frequency vibrations while driving.

Question: What about maintenance of struts on a vehicle?

Answer: Struts and shocks are an item that doesn't necessarily have to be replaced at any particular interval. The wear and tear on a strut assembly is dependent on the type of vehicle you own and how/where it is driven. Many strut assemblies can last 5-10 years without any required repair or replacement given the right driving conditions. However, some car experts suggest replacing them at 100,000 anyways. In my experience this is not the case. A Mazda Protege I once owned needed the shocks replaced at less than 80,000 miles however the components on my Honda Civic lasted much longer.

With significant variability based on driving conditions and vehicle make/model, struts and/or shocks should probably be inspected at every oil change. Look for wear on the strut itself or on the rubber components. Rust and corrosion can reduce performance of the suspension system. Also look for leaning or sagging in your vehicle and perform a bounce test to see if the struts respond properly. Push down as hard as you can on a corner of your vehicle. Once you let go if the car bounces a lot it may be time to replace the shocks and struts. If there is no (or limited) bounce, then your shocks and struts may be performing correctly.

Question: Should I overhaul or replace a manual transmission at 200,000km?

Answer: In general, vehicles with manual transmissions should have the transmission oil changed every 50,000-65,000 kilometers (30,000-40,000 miles). In addition, the clutch will also need to be replaced regularly depending on how the vehicle is driven. Trucks that tow heavy loads and race cars need to have their clutch changes more frequently. There is no set interval on replacing a clutch, however, when you feel the clutch starting to slip on a consistent basis, it may be time to replace it.

One of the main reasons transmissions fail is due to heat accumulation caused by friction. Heavy loads or fast speed changes can shorten the life of the transmission. If the transmission fluid is changed regularly (and high-quality fluid is used) a gearbox can easily last 240,000-320,000 kilometers (150,000-200,000). A manual transmission overhaul is needed if gears are starting to stick, you hear regular grinding or transmission chatter, or if the seals/bearings are leaking. When it comes to the transmission itself, a lot of this depends on the vehicle and how it is driven.

Automatic transmissions are more complicated and tend to have a shorter lifespan than manual ones for this reason.

© 2012 Christopher Wanamaker

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