How to maintain a car engine

Updated April 30, 2022
  • Change the engine oil every 5K miles or as recommended to keep the oil clean and moving parts inside the engine well lubricated.
  • The oil must be kept at the proper level between oil changes; top it up if the level drops.
  • Synthetic oil offers a better protection, especially in a turbocharged engine.
  • Keep an eye on the engine coolant level in the overflow tank and repair leaks in the cooling system before a loss of coolant will cause the engine to overheat.
  • Change the air filter every 15K miles.
  • Change the spark plugs at recommended intervals or every 60K-100K miles.
  • For a diesel engine, change the fuel filter at least every 30,000 miles.
Your engine is the heart of your car and is expensive to repair or replace, but it can last long with good care. We have seen many engines with over 200K-300K miles running like new. What is the secret?
Car engine Car engine.
Your engine has many moving and rotating parts. These parts need to be well lubricated by engine oil. As you drive, the oil degrades and the level drops. The increased friction causes accelerated wear. What are the signs that your car needs an oil change? You can check the engine oil level and condition with the dipstick. If it looks too dirty, have the oil change done. Read here on how to check engine oil: Simple car maintenance checklist.

How often should you check your oil?

Checking  engine oil Check engine oil level.
The goal is to maintain the proper level of oil. Car manufacturers recommend checking the oil level on a regular basis, some manufacturers advise doing it every time you refuel. Many modern cars consume some amount of oil between oil changes. If you check the level after 1,000 miles and it is close to the "Low" mark, check it more frequently and top up as needed. Oil leaks are another reason to check the level more often.

Some cars barely use any oil between oil changes. If you check the level after 3,000 miles and it's still close to full, then you know when you should check it the next time.

Is there a warning light for low oil?

No, most cars don't have any warning light that will warn you if the oil level is low. There is the low oil pressure warning light, but by the time it comes on, the level could be so low that it's not even enough to keep the minimum oil pressure. The proper oil pressure, as well as the level are vital for lubrication of all moving parts.

Many cars have an oil change reminder message, but it's based on the mileage driven or time since the last oil change. The oil change reminder doesn't know the oil level.

How to prevent the engine from overheating

Engine overheated Have the vehicle checked if the engine temperature rises more than normal
Overheating is the source of many engine problems and in worst cases, it can result in major engine repairs or even replacement. One of the common problems is when the coolant level drops due to leaks, which causes the engine to overheat. Other reasons for overheating include a failed water pump, radiator fan or the thermostat.

How can you prevent overheating? Keep the cooling system topped up and have the vehicle checked if the engine temperature rises more than normal. Read: Car maintenance checklist: how to check the coolant level.

Watch out for coolant leaks and repair them before the coolant drops to dangerous levels. Keep the front of the radiator clean from debris, as the coolant is cooled down by the air flow passing through the radiator fins.

Synthetic oil offers a better protection, especially in a turbocharged engine

Synthetic oil Synthetic oil
Synthetic oil lasts longer, provides better lubrication at below-zero temperatures and can withstand higher temperatures in a turbo engine.

However, if your high-mileage car doesn't have a turbocharger and doesn't require synthetic oil, switching from mineral to synthetic oil is not always worth the extra cost.

How long can you go between oil changes with synthetic oil?

Synthetic oil does lasts longer, but what about products of wear? Rotating and moving parts inside the engine will wear, whether you use regular or synthetic oil. If you drive longer between oil changes, the tiny metal particles and other products of wear mix with oil, reducing its lubricating ability. On top of this, they clog up the oil filter, restricting the oil flow, which in turn, further increases friction. We recommend keeping oil change intervals close to what is recommended by your car manufacturer regardless of type of oil used.

Do oil additives really help?

Engine oil additive Car manufacturers advise against using oil additives
Most car manufacturers don't recommend using any additives, but you will find many people swear by them. We had tried several products in different engines. Some oil additives didn't have much effect, but others actually worked.

For example, there was a four-year old Honda Accord that was consuming more than 2 quarts of oil between oil changes. Since the engine overall was in good shape, we suspected that the oil rings were stuck in their grooves due to carbon build-up. We added an oil additive that was said to "help free sticking oil rings" and it worked. After this, the oil level in this Honda stayed almost the same between oil changes.

Is your air filter clean?

Dirty vs new air filter Dirty vs new air filter
An engine air filter prevents dust and other debris from being sucked into your engine. A clogged-up air filter restricts the air flow, causing lack of power when passing or accelerating. An old air filter can actually collapse or rip through, allowing sand and dust into the engine.

An air filter is typically replaced every 15,000 miles or more often if you drive on unpaved roads. Replacing an air filter can cost from $30 to $50 or can be done DIY as in most cars, it's an easy job.

How do you know if your spark plugs need changing?

Conventional spark plugs Old conventional spark plugs have a larger electrode gap.
Spark plugs ignite the air-fuel mixture in the combustion chamber, see the diagram. Some cars have conventional spark plugs, some have long-lasting (Iridium/Platinum) spark plugs. Conventional spark plus wear out with mileage and the electrode gap increases, see the photo.

The larger gap requires higher voltage to produce a spark. This adds load on the ignition coil and a spark plug wire. Eventually an ignition coil fails or a spark plug wire shorts out causing the engine to misfire. Conventional spark plugs need to be replaced at lower mileage, before 60,000-80,000 miles.

Many modern cars have long-lasting platinum- or iridium-tipped plugs. The electrode gap stays the same longer, but spark plugs can get contaminated.
Iridium spark plugs New vs. old Iridium-tipped spark plugs.
We have seen iridium-tipped spark plugs last for over 160,000 miles. However, we have also seen many cars where contaminated spark plugs were causing ignition coils to fail much earlier.

The symptoms of worn-out or contaminated spark plugs include rough idle, occasional misfiring at start up and acceleration. Often, however, there is no symptoms until an ignition coil fails. Read more about ignition coils problems, when to replace and repair costs.

Does your car have long-lasting spark plugs? One way is to check the maintenance schedule for your car. If it says replace at 120,000 miles, it's probably long-lasting ones. You also can check in the Specifications section of your owner's manual, it will say it's iridium or platinum-tipped or it will give you the part number. Google the part number and it will tell you what kind of spark plugs you have. Long-lasting spark plugs are more expensive, around $25-$40 apiece. Conventional spark plugs go for $8-$16 each.

Does your engine need a tune-up?

Engine tune-up Common tune up items: spark plugs, spark plug wires, air filter and throttle body service
An engine tune-up needs to be done every 60,000 to 90,000 miles. In modern cars, a tune-up may include changing spark plugs and an air filter. Iridium- or platinum-tipped spark plugs last longer, but we have seen them getting contaminated to the point where they cause an engine to misfire. If your car has spark plug wires and fuel filter, they may also need to be replaced.

In some cars, the PCV valve can fail, causing increased oil consumption. If it's a common problem for your make and model, the PCV valve need to be checked during a tune-up. Your mechanic may also suggest cleaning the throttle body. A very dirty throttle body can cause too low or too high idle speed and the Check Engine light. See how a dirty throttle body looks compared to new.

Often, problems with idle speed happen after a car battery has been replaced or disconnected. When the battery is disconnected, an engine computer resets some learned values, including the throttle angle. In many cars, the idle has to be re-learned after disconnecting the battery.

Carbon buildup on intake valve Carbon buildup on the intake valve
In some high-mileage cars with direct fuel injection, carbon deposits, accumulated on the intake valves (see the photo) can cause misfiring. If your car has a direct injection, your mechanic may suggest cleaning intake valves during a tune-up.

There are several ways to clean intake valves. It can be done with a special solution that sprays inside the intake while the engine is running or manually. Cleaning valves manually is more effective, but it requires more labor. Check out these YouTube videos for more info.

When to replace the timing and serpentine belt?

Timing belt in good condition Timing belt
Not all cars have a timing belt. Many modern cars have a timing chain instead of a belt. You can check your maintenance schedule, it usually mentions when a timing belt must be replaced or at least inspected. The timing chain doesn't need regular replacement. In most cars, timing belt replacement intervals vary between 60,000 and 105,000 miles (96,000-168,000 km). Read more about the timing belt.

All gasoline- or Diesel-powered cars have at least one serpentine belt. An old serpentine belt can break, which means your car will have to be towed in. If a serpentine belt shows signs of wear or is found to be soaked in oil, it must be replaced. Read more: Serpentine Belt: problems, signs of wear, when to replace, noises.