The Importance of Car Maintenance: A Complete Guide

Everything you need to know about car maintenance and how to use your maintenance checklist

All the services your car needs are listed in your owner’s maintenance guide. But the guide doesn’t explain why those services are needed nor does it explain what will happen if you don’t perform them. That’s why I’ve written this car owner’s maintenance guide to explain what the carmaker’s guide really mean.

Maintaining your car by performing the recommended services is expensive is expensive, but not maintaining your car is more expensive!

The first thing you need to know about maintenance guides: There are TWO service schedules; one is for Normal Service and one for Severe Service.

Most car owners follow the normal schedule even though their driving habits fall into the severe service category.

If you live in a large city and your trips are usually less than 5 miles, you should be following the Severe Service Schedule.

What is the definition of severe service?

Every carmaker has a slightly different definition of severe service. Find the definition for your vehicle in your owner’s maintenance guide.

Subaru’s definition of severe service

• Repeat short-distance driving is severe service

If you drive short distances on a regular basis, especially in stop-and-go traffic you need to change your oil according to the severe service schedule. Why? Short trips are much harder on your oil than long commutes or extended highway drives. Short trips never let your engine get up to full operating temperature, so the oil never gets hot enough to evaporate off the contaminates generated during a cold start. Those contaminates can turn your oil into sludge and acids and degrade your oil’s anti-corrosion additives much faster.

• Driving short distances in extremely cold weather is severe service

Starting a cold engine requires more fuel and some of that extra fuel, along with other combustion byproducts (water and soot) gets pushed past the piston rings and into the crankcase. If you take a short trip after a cold start, you’ll never evaporate off those liquids or filter out the soot generated during the cold start. The result? Your oil develops acid and sludge deposits and your engine experiences accelerated internal corrosion. That’s why most carmakers recommend more frequent oil changes if you take short trips in cold weather.

• Driving on bumpy muddy roads is severe service

Bumpy roads cause suspension components to cycle more often than when driving on smooth roads. That causes accelerated wear on suspension bushings, sway bar links, shocks, struts, ball joints, and tie rods. Mud splash makes those parts wear out even faster. If you drive in these conditions, you’ll need more frequent inspections to catch the wear early and avoid accelerated tire wear or serious on-the-road failures.

• Driving in areas where road salt is used is severe service

Salt corrodes brake and fuel lines, suspension components, and critical frame/body components. Performing more frequent inspections and applying rust remediation products can prevent costly rust-related failures.

• Repeat trailing towing or hauling heavy loads is severe service

Trailing and hauling heavy loads puts added stress on the engine, transmission, drive shafts, suspension components, and wheel bearings, requiring more frequent inspections and service (fluid changes).

• Repeat driving in dusty conditions is severe service

Dusty conditions clog engine and cabin air filters faster and can reduce engine and transmission cooling, requiring more frequent filter changes and radiator/cooler cleaning.

• Driving/living in high-humidity coastal or mountainous areas

High humidity causes brake and clutch fluids to adsorb more moisture, reducing its effectiveness. It also corrodes body, frame, and suspension parts, requiring more frequent inspection and rust remediation. Driving in mountainous areas requires more frequent brake inspections to spot brake wear early.

What’s the definition of a short trip?

It varies by carmaker, but generally speaking, it’s any trip that’s less than 5 miles (in Spring, Summer or Fall) or less than 10 miles in Winter conditions.

It’s not just miles that count, time between services counts as well

Here’s why maintenance checklist guides list services and inspections based on time and mileage

When it comes to fluid service, most maintenance guides list both a time and mileage interval. For example, an engine coolant change is often listed as 100,000 miles or 10 years, whichever comes first.

Why is time in service so important? Because the anti-corrosion, and pH balancing additives in fluids start to deteriorate once they’re put into service. Carmakers know how long these critical additives last, even if you haven’t racked up enough miles to justify changing the fluid. That’s why fluids must be changed on time or mileage, whichever comes first.

The same applies to oil changes. All carmakers list a mileage and a time interval, whichever comes first. Read on to find out why time is so important when it comes to oil changes.

How deep do you want to get with this article? — Just the facts or Tell Me The Whole Story

Some car owners just want to know what maintenance to do and when to do it. Section 1 is for those readers. Others want to know why the maintenance schedules are set up that way and why particular services must be done. Section 2 is for those readers

Section 1 — Just the facts

Just the basics about Oil changes

The carmaker, not the oil company, your friends or Internet know-it-alls know how long oil lasts in each engine and driving condition. If you use the recommended oil and check your oil level at least once a month and top off when you’re more than 1/2-quart low, then you can rely on the oil change intervals listed in the maintenance guide.

However, if you drive your car when it’s low on oil, you’ll wear out the remaining oil much faster, or even run out of oil before your car is due for its next oil change. Driving on worn-out oil causes accelerated engine wear.  It’s your responsibility to check your engine’s oil level at least once a month and top off the oil when needed.

The same rule applies if your car is equipped with an oil life monitoring (OLM) system. It assumes you’ve used the recommended oil, checked your oil level, and topped off when needed. If you don’t do that, all bets are off on the accuracy of the (OLM)

What you need to know about Spark plugs

All spark plugs wear out and must be replaced with the recommended type and at the recommended mileage. The spark plug change interval is listed in your maintenance checklist.

Trying to squeeze more miles out of old spark plugs is self-defeating. Worn spark plugs dramatically reduce your gas mileage, cause no-starts in cold weather, and can damage other expensive ignition components.

Replacing engine coolant on time is critical to the life of your cooling system

Coolant life is based on time and mileage. Continuing to drive on worn-out coolant allows corrosion to set in and that corrosion can damage the heater core ($1,500 repair), radiator ($600 repair), water pump ($750 repair), and even head gaskets ($3,5000 repair).

Follow the maintenance guide recommendation for coolant change intervals and get a full coolant flush, not a radiator drain and fill, when it’s due. Make sure the shop uses the carmaker’s recommended coolant and not a “universal coolant.” Shops use universal coolant so they don’t have to stock the coolant recommended by the carmaker. However universal coolants are not the same as factory-recommended coolants. Insist on the proper coolant.

Brake inspections actually save money

Brake components operate in a harsh environment, causing the sliding components to rust and seize. Once rust sets in, the brake pads and rotors wear out quickly. However, if caught early, the shop can remove the rust, lubricate the moving parts, and prevent costly early wear. Skipping brake inspections and waiting until brakes make noise, usually results in brake repair bills in the $600- $1,000 range.

Brake fluid must be changed because it accumulates moisture

Many carmakers recommend routine brake fluid flushes due to moisture infiltration. Water in brake fluid decreases braking ability, and worn-out anti-corrosion additives allow rust to form, which damages the system from the inside out. In addition, the anti-corrosion and pH balancing additives in brake fluid wear out.  Brake fluid flushes cost far less than the damage caused by corrosion.

Drive belts wear out and must be changed before they break

It’s really simple; rubber drive belts wear out. Older neoprene belts cracked as they aged, so it was easy to do a visual check for wear. But newer belts are made with a different rubber that doesn’t crack. They must be checked with a wear gauge and replaced if they fail the test. Worn belts can cause squeals and screech noise as they slip. A worn belt can break unexpectedly, leaving you stranded

Shocks and struts provide more than a comfortable ride

A shock/strut’s main job is to dampen bounce when you hit a bump. So they keep your tires on the road. Worn shocks and struts allow tires to bounce and that reduces vehicle stability. In addition, worn shock/struts increase your stopping distance, wear out your tires and suspension components faster and give you a less comfortable ride.

Why checking tire pressure monthly is so important

There’s a direct relationship between tire wear and tire pressure. Under-inflation causes rapid wear on the inner and outer edges of the tire, while over-inflation causes rapid wear on the center tread. In addition to rapid wear, under/overinflation causes increased stopping distances and increases the likelihood of hydroplaning on wet surfaces.

All tires lose approximately 1-2-psi per month, so checking monthly and topping off will keep you at the correct pressure.

Outdoor temperature changes affect tire pressure. Tire pressure changed 1-psi for every 10°F change in ambient temperature. If you fill your tires to the recommended pressure when it’s 20°F in March, they’ll be overinflated by 6-psi. when it hit 80°F in late April.

You’ll find the factory-recommended tire pressure on a label posted on the driver’s door pillar. Never inflate your tires to the maximum tire pressure listed on the tire sidewall.

Everything you need to know about suspension and steering systems

Everything you need to know about brakes

Everything you need to know about tires

by a significant amount.
2) Worn spark plugs cause no starts, especially in cold weather. So you’ll have to pay for a tow (average cost $200), a diagnostic charge ($150) AND the cost of new spark plugs.
3) Worse yet, driving on worn spark plugs can damage other expensive components like ignition coils or even an expensive ignition module or computer. So you’ll need a tow ($200), a diagnostic ($150) at least one ignition coil ($175) and possibly a computer or ignition module ($500-$1,200), AND, new spark plugs.

What happens if you don’t change your transmission fluid or differential oil?

Not changing your transmission fluid, CVT fluid, or differential fluid can cause complete transmission, CVT, or differential failure. A transmission rebuild costs around $4,600 and a differential replacement can cost upwards of $3,000, depending on the vehicle. In comparison, a transmission fluid change costs around $200. If the carmaker recommends a transmission fluid change every 30,000 miles, you’ll pay $1,400 over 200,000 miles versus $4,600 for a transmission rebuild and then fluid changes every 30,000 miles after the rebuild.

What happens if you don’t change your engine coolant?

Engine coolant does more than keep your engine from freezing in the winter or overheating in the summer. Coolant contains anti-corrosion additives and pH balancing additives. They wear out over time and when they do, corrosion sets in. Coolant replacement costs about $225 every 100K miles

1) Driving on worn out coolant can cause heater core corrosion and failure in winter. Heater core replacement requires removing the entire dash at a cost of around $1,800. During the heater core replacement, the shop will still have to replace the coolant.
2) Driving on worn out coolant cause cause radiator corrosion, clogging and engine overheating. A new radiator costs around $600 and overheating can cause head gasket failure, costing almost $3,000.
3) Worn out coolant can also cause early water pump failure and corroded heater hose/tubing failure, costing at least $800 on most vehicles.

What happens if you don’t inspect/change shocks/struts?

Struts typically last 80,000-120,000 miles depending on the road conditions in your area. In addition to causing an uncomfortable ride, worn struts/shocks causes your tires to wear out about twice as fast as normal and cause accelerated suspension component wear as well. So you’ll waste about $400 in lost tire wear, about $800 in suspension component wear, and you’ll still have to replace your struts/shocks. You obviously don’t save money by driving on worn struts/shocks.

There are actually TWO service schedules in your owner’s maintenance guide. One is for Normal Service and the other if for Severe Service.

How long your trips last, and how you drive determines which schedule you must follow

FACT: Mose car owners follow the Normal Service Schedule schedule. But the way most urban car owners drive their car means they should be following the Severe Service schedule.

If your driving falls into the severe service category, but you follow the normal service schedule, you’re going to wind up with more breakdowns and you’ll shorten the life of your engine and transmission. Those are costly items to replace, so it actually pays to follow the correct service schedule

So what exactly is the definition of severe service?

Every carmaker has slightly different definition for severe service, but here’s typical description from Subaru.

• Repeat short distance driving is severe service

It you drive short distance on a regular basis, especially in stop and go traffic you need to change your oil according to the severe service schedule. Why? Because short trips are much harder on your oil than long commutes or extended highway drives. Short trips never lets your engine get up to full operating temperature, so the oil never gets hot enough to evaporate off the contaminates generated during a cold start. Those contaminates can turn your oil into sludge and acids and degrade your oil’s anti-corrosion additives much faster.

• Driving short distances in extremely cold weather is severe service

Starting a cold engine requires more fuel and some of that extra fuel, along with other combustion byproducts (water and soot) get pushed past the piston rings and into the crankcase. If you take a short trip after a cold start, you’ll never evaporate off those liquids or filter out the soot generated during the cold start. The result? Acid and sludge deposits and  accelerated internal corrosion. That’s why most carmakers recommend more frequent oil changes if you take short trips in cold weather.

• Driving on bumpy muddy roads is severe service

Bumpy roads cause cause suspension components to cycle more often than when driving on smooth roads. That causes accelerated wear on suspension bushings, sway bar links, shocks, struts, ball joints and tie rods. Mud splash makes those parts wear out even faster. If you drive in these conditions, you’ll need more frequent inspections to catch the wear early and avoid accelerated tire wear or serious on-the-road failures.

• Driving in areas where road salt is used is severe service

Salt corrodes brake and fuel lines, suspension components, and critical frame/body components. Performing more frequent inspections and applying rust remediation products can prevent costly rust-related failures.

• Repeat trailing towing or hauling heavy loads is severe service

Trailing and hauling heavy loads puts added stress on the engine, transmission, drive shafts, suspension components and wheel bearings, requiring more frequent inspections and service (fluid changes).

• Repeat driving in dusty conditions is severe service

Dusty conditions clog engine and cabin air filters faster, and can reduce engine and transmission cooling, requiring more frequent filter changes and radiator/cooler cleaning.

• Driving/living in high humidity coastal or mountainous areas

High humidity causes brake and clutch fluids to adsorb more moisture, reducing its effectiveness. It also corrodes body, frame and suspension parts, requiring more frequent inspection and rust remediation. Driving in mountainous areas requires more frequent brake inspections to spot brake wear early.

What’s the definition of short trip?

It varies by carmaker, but generally speaking, it’s any trip that’s less than 5 miles (in Spring, Summer or Fall) or less than 10 miles in Winter conditions.

It’s not just miles that count, time between service counts as well

Here’s why maintenance checklist guides list services and inspections based on time and mileage

All maintenance guides list time and mileage intervals for items that should be replaced and components that should be inspected. For example, an engine coolant change is often listed as 100,000 miles or 10-years, whichever comes first. Time is just as important as mileage. Why? Because the additives in fluids deteriorate over time and once they’re no longer effective, you wind up with corrosion and accelerated wear.

The same applies to oil changes. All carmakers list a mileage and a time interval, whichever comes first. Read on to find out why time is so important when it comes to oil changes.

Everything you need to know about fluid changes

What you need to know about oil change intervals.

Mobil 1 Extended Performance Motor Oil promises 20,000 miles between oil changes. But did you read the * (fine print)? It’s 20,000 miles or 1 year, whichever comes first. And, if your vehicle is covered by a warranty; factory or extended warranty, you have to change your oil according to the carmaker’s recommended oil change schedule, which will be far more often than every 20,000 miles or 1 year. Plus, the 20,000 miles recommendation goes out the window if you drive in a way that would normally be considered severe service. Plus, you must routinely check your oil level and top off when needed

As discussed above, oil change intervals are based on how you drive, how long the trips are and whether you’re hauling heavy loads. But oil change intervals are also based on the engine design. Some engines, by their very design, require more frequent oil changes. For example, some engines with turbochargers require more frequent oil changes due to the extreme heat generated by the turbo. Yet other engines with turbos can go longer between oil changes because they’re equipped with oil coolers.

There is no one-size-fits-all advice when it comes to oil change intervals. Oil change intervals are set by the carmaker, not self-proclaimed “Internet experts,” family “know-it-alls,” or even extended oil change intervals claimed by oil brands.  You can’t even trust the claims made by motor oil manufacturers unless you read the fine print. Don’t take oil change advice from self-proclaimed “experts” on the Internet or family “know-ot-alls.”

Bottom line: consult your maintenance checklist and follow the proper service schedule.

Everything you ever wanted to know about motor oil

Motor oil has 4 jobs: Lubricate to prevent wear, cushion to prevent metal-to-metal contact, remove heat from high friction areas, and clean your engine.

To accomplish those four jobs, motor oil contains specific additives in addition to the base oil. For example, most motor oils contain around 75%-80% base oil and 20%-25% additives.

Motor oil can remain stable in the bottle for five or more years. But once it’s in your engine, the clock starts ticking. The additives degrade from exposure to air (oxygen), heat, friction, water, and acids. Once the degradation starts, it continues even when your engine is off. In other words, the additives are always working and they are used up in the process.

That’s why all carmakers recommend changing your oil based on mileage AND time. If your owner’s maintenance guide calls for oil changes every 6,000 miles OR six months, whichever comes first, change your oil at 6 months even if you haven’t driven 6,000 miles. Why? Because the additives have been working for 6 months and they’re most likely depleted.

Here are the most common motor oil additives, what they do, and how they degrade

Anti-oxidants

Exposure to oxygen causes the base oil to break down and form acids and sludge in your engine. Oxidation happens at all temperatures, but accelerates at when your engine is fully warmed up. Oxidation also increases in the presence of  water, wear metals and combustion byproducts present in blow-by gasses (air, fuel, and exhaust that seeps past the piston rings and into the crankcase).

Anti-oxidants (oxidation inhibitors) are used to extend the operating life of motor oil. But they are sacrificial additives, i.e. they are consumed while performing their duty

Rust and Corrosion Inhibitors

Rust and corrosion inhibiting additives work by neutralizing the acids that form in the crankcase and by providing a protective chemical barrier on metal surfaces to repel moisture. Once these additives are exhausted, corrosion sets in.

Viscosity Index Improvers

All motor oil thins as it heats up. To reduce thinning, all motor oils contain Viscosity Index Improvers (VII) made from a “watch spring” type of polymer that “unwinds” as it heats up. So the VII takes up more space, reducing the oil’s tendency to thin. As the oil cools, the VII molecules “wind back up” to help the oil flow better. VII is what allows an oil to be have different viscosities at different temperatures, like 5W-30.

However, VII molecules degrade when exposed to high loads in gears and bearings. The “squishing” forces in gears and bearings can permanently deform the molecule or cut into smaller pieces. At that point, the additive can no longer perform its intended function. So the oil becomes too thin at normal operating temperature, providing less protection against wear.

Like other motor oil additives, VII is sacrificial; it gets damaged while doing its job.

Anti-wear Additives

Anti-wear additives are activated by the high heat caused when metal-to-metal contact occurs. The anti-wear additives “melt out of suspension” and react chemically with the metal surfaces to form a film that minimizes wear.  They also help protect the base oil from oxidation and the metal from damage by corrosive acids. Like most other additives, the anti-wear additives get used up the more you drive.

Extreme Pressure (EP) Additives

EP additives chemically react with metal (iron) surfaces to form a sacrificial surface film that prevents metal parts from welding together during periods of metal-to-metal contact.

Detergent Additives

Detergents prevent deposits from forming on metal components and they neutralize acids that form in the oil.

Dispersant Additives

Dispersant additives keep soot particles suspended in the oil so they can be captured by the oil filter and not settle out of suspension to form sludge deposits.

Anti-foaming Additives

Rotating engine parts whip air in the oil. Foamed oil can’t carry out its job of removing heat from high friction areas. So anti-foaming agents reduce oil’s surface tension causing the bubbles burst. Because anti-foaming agents reduce foaming, they also reduce oxidation that occurs when oil bubbles carries oxygen around the engine.

Friction Modifiers

Friction modifiers help make engine oil more slippery to reduce friction and improve fuel economy.

Demulsifiers

All blow-by gasses contain water (by-product of combustion) which winds up in crankcase oil. When oil and water mix, they form a thick emulsion that begins the process of sludge formation. A demulsifier additive prevents the formation emulsion by separating the water from the oil.

Tackifier Additives

Tackifier additives prevent the oil from flinging off of the metal surfaces they’re supposed to protect.

Anti-oxidants, rust and corrosion inhibitors, detergent, dispersant and demulsifier additives work 24/7 to protect your engine and they all degrade once they’re exposed to oxygen, heat, fuel, and water.

Everything you ever wanted to know about Power Steering Fluid

The hydraulic power steering units used in older vehicles use several types of power steering fluid. Some use transmission fluid like Dexron III, or ATF+4 (for Chrysler vehicles). Still others use a special fluid you can only get from the dealer, like Honda power steering fluid.

The fluids vary in their viscosity and additive packages. Most carmakers don’t list a change interval for power steering fluid because it’s considered a “lifetime” fluid. However, the additives do wear out, and the fluid picks up metallic debris as you rack up the miles. If you want to be proactive, it’s a good idea to perform a power steering fluid flush once every 100,000 miles.

SCAM ALERT: Many shops recommend a power steering fluid flush every 30,000 miles. There is no scientific basis for that recommendation! Not a single carmakers agrees with that recommendation. Do not fall for this! It’s an unnecessary service designed to flush your wallet, and it provides no benefit to your vehicle. Say no to this service and find a more reputable shop.

Everything you ever wanted to know about Differential Fluid

Everything you ever wanted to know about Engine Coolant

Everything you ever wanted to know about Brake fluid

Everything you need to know about belts

Everything you need to know about Spark plugs and ignition systems

Everything you need to know about suspension and steering systems

Everything you need to know about brakes

Everything you need to know about tires

Any time you take your car in for service, the service adviser is going to recommend additional services. That’s their job; to upsell you on services. Some are needed, but most are not. They’re considered “wallet flushing” services designed to clean out your wallet and generate more revenue for the shop. So the question is this: How can you properly maintain your car without getting suckered into these unnecessary services? Well, it’s all there in your car maintenance guide; if only it was written in owner friendly language.

That’s what this article is all about; explaining what the carmakers’ car maintenance guide actually means for you the car owner.

Most unexpected repairs are caused by owner’s not following the carmaker’s maintenance schedule.

Yes, you read that correctly. Not performing the recommended serviceds

Not checking things

Not understanding the difference between normal wear and tear and an unexpected repair.

Normal wear and tear

Tires, brakes, struts/shocks, CV joints, steering parts, belts, battery, coolant, brake fluid/clutch fluid, transmission fluid, differential fluid.  Rusted brake lines, fuel lines.

Next, understand the importance of each of the inspect and replace services.

air filter

brake fluid

Brakes and traction control

cabin air filter

clutch fluid

Clutch/MT

coolant

cooling system

disc brake system

drive belt

engine oil

transmission cvt fluid

differential fluid

transmission fluid manual

fuel delivery and air induction

fuel filter

oil filter

spark plug

tires

Wheel bearing

steering

suspension

tires

battery