Spark Plug Health – Is directly linked, to overall engine performance

Spark Plug Health - Is directly linked, to overall engine performance
Spark Plug Health - Is directly linked, to overall engine performance

Spark plug replacement intervals, on today’s engines is getting longer all the time.

Because, spark plug health, is directly linked to overall engine performance; it stands to reason, weak or bad spark plugs, can lead to problems.

But, there is a risk, if the spark plugs are neglected for too long.

That’s why spark plug health, is so important to overall engine performance.

Normal Wear And Tear (Healthy Engine)

Spark plugs don’t last forever, even if your engine is in perfect condition.

The two biggest reasons are:

Spark Plug Deposit Buildup

When deposits form on spark plugs from interaction with the air-fuel mixture; it can lead to pre-ignition of the fuel.

Deposit Buildup
Spark Plug Deposit Buildup

That means a jerky and unreliable supply of energy for your car.

Expanding, Harder-To-Jump Gap

When a spark plug ignites, it has to travel across a gap of space; in order provide the right level of combustion at the right moment. As spark plugs age, this gap widens as a result of; extreme temperatures, debris and normal wear and tear. If the gap is too far apart, combustion will be erratic or ineffective.

Excessive Spark Plug Gap
Excessive Spark Plug Gap

As the electrodes wear, the voltage required to fire the plugs continues to go up. And, will eventually lead to misfires and; possible damage to the ignition coils and/or spark plug insulator boots. The (OBD) system will detect ignition misfires and turn on the Check Engine light.

Spark Plug Life Span (Healthy Engine)

Most spark plugs have a factory service interval of 100,000 miles; though some may be as much as 120,000 miles.

Platinum And Iridium Spark Plugs
Platinum And Iridium Spark Plugs

Long-life platinum and iridium spark plugs, will typically last up to 100,000 miles or longer; provided the engine isn’t using oil or doesn’t spend a lot of time idling.

What Can Shorten, Spark Plug Life Span

Any or all, may be the cause:

  • Oil in the Combustion Chamber
  • Improperly Gapped Spark Plugs
  • Carbon Build Up
  • Overheating
  • Mechanical Damage

Spark Plug health, can be shortened, by frequent short-trip driving and idling. Including internal engine problems, that increase oil consumption (such as worn valve guides or piston rings).

What Are The, Early Failure Warning Signs

Symptoms of bad spark plug health, can include:

  • Reduced Gas mileage
  • Lack of Acceleration
  • Hard Starting
  • Engine Misfires
  • Rough Engine Idle

Spark Plug Replacement, Caution

Replacing spark plugs at 100,000 miles, can be troublesome on some applications. When a spark plug has been in the cylinder head for that many miles; carbon and corrosion can make it difficult to remove. There is a risk of damaging the threads in aluminum cylinder heads. Many spark plugs have nickel-plated threads on the plug shell. Also, helping to prevent corrosion; between the steel threads on the plug and the aluminum threads in the cylinder head.

No Corrosion Resistance
Corroded Spark Plug

Some spark plugs have a black oxide coating on the shell to inhibit corrosion. But, it’s not as effective as a nickel coating. Plain uncoated spark plugs offer, no corrosion resistance whatsoever, when installed in aluminum heads. Dissimilar metals can react over time, causing the spark plug, to stick in the head.

The use of anti-seize compound on spark plug threads to make future replacement easier; is not recommended for two reasons:

  1. Anti-seize acts like a lubricant, which increases the risk of over-tightening the spark plug. As a result, damaging the threads in the cylinder head.
  2. It can contaminate the electrode causing the plug to foul and misfire. Spark plugs should be installed dry and tightened to specifications.

What Type Of Spark Plug Should I Use

The best guide is the manufacturer’s recommendation for your vehicle. Because, this particular service varies from brand to brand and model to model.

In general, it’s best to replace spark plugs, as part of preventative maintenance, based on manufacturer’s specifications. This can help save you from costly repairs, as driving with misfiring spark plugs; could put undue stress on your car’s catalytic converter (the engine’s exhaust cleaner).

Spark Plug Health Comparison Old And New
Spark Plug Health Comparison Old And New

It’s during the last 20% of a spark plugs life that misfires and incomplete combustion occurs most frequently. So, changing them before you hit that last stretch can save you money, time and frustration.

Yes, today’s spark plugs can be expensive. And, you see that when you pay for them. But, the savings in fuel and related failures can; far exceed that price during the life of new spark plugs.


As your car gets older, you may need to replace the spark plugs more frequently. This is not a difficult project, but it can easily appear tricky to the newbie DIY’er. If you are starting to experience a loss of power; poor fuel economy, misfires, rough idling, etc.; it may be due to worn-out spark plugs.

Reading Spark Plug Condition
Reading Spark Plug Condition

So, your spark plug health can provide valuable information about your vehicle’s performance; and can predict potential problems. Learning how to read a spark plug is quick and easy. In short, the reading of a spark plug involves; evaluating the condition and color of the tip of the spark plug. Spark Plug Color – Evidence Of What Is Happening Inside The Engine

Head off small problems before they get out of control !

Thank You !