Has your trusted vehicle started to show its age? Perhaps the engine doesn't sound as robust as it once did, or you've noticed a dip in fuel economy. These are common issues for vehicles that have traveled many miles. The solution might be simpler and more affordable than you think. Understanding which spark plugs are the best for high-mileage cars can restore performance and efficiency.
Let's examine different types of spark plugs, their materials, and what makes a particular plug suitable for a car that's been around the block a few times.
High-Mileage Engine Needs
An engine with over 75,000 miles is generally considered high in mileage. As engines age, their internal components experience wear. This wear can lead to compression loss, oil consumption, and carbon buildup. These conditions alter the environment inside the combustion chamber, affecting spark plug performance.
For instance, oil can leak past worn piston rings and foul the spark plugs. Carbon deposits from incomplete combustion can also coat the electrodes. This contamination insulates the spark plug, which makes it harder for the spark to jump the gap. The result is a weak or inconsistent spark, which leads to misfires, poor fuel economy, and increased emissions.
Types of Spark Plugs
The type of material in the center electrode sets spark plugs apart. It influences the plug's durability, performance, and price. Let's look at the four primary types.
Copper Spark Plugs
Copper spark plugs are the traditional choice for ignition systems. Their nickel-alloy coating covers a copper core, providing superior electrical conductivity for a powerful spark.
These plugs are affordable, but their main drawback is their lifespan. The nickel alloy wears down relatively quickly, so you'll need to replace them more often, every 20,000 to 30,000 miles. For a high-mileage vehicle, this frequent replacement schedule might be a nuisance.
Iridium Spark Plugs
Iridium is an extremely hard, precious metal. Iridium spark plugs have a fine-wire center electrode, which requires less voltage to create a spark. This efficiency allows for a more consistent and powerful spark, which improves ignition and fuel efficiency.
The hardness of iridium also means these plugs last much longer than copper or platinum plugs. You can expect an iridium plug to last up to 100,000 miles or more. Their durability makes them an excellent choice for high-mileage cars, because they perform better over a long period despite the harsh conditions inside an aging engine.
Platinum Spark Plugs
An upgrade from copper plugs, platinum spark plugs have a disc on the center electrode. Since platinum is a more durable material than nickel alloy, these plugs have a longer lifespan, often reaching up to 60,000 miles.
There are single platinum and double platinum plugs. Single platinum plugs have a platinum-tipped center electrode. Double platinum plugs have platinum on both the center and ground electrodes. Designed for "waste spark" ignition systems, they fire two plugs simultaneously.
Double Platinum Spark Plugs
This design is particularly beneficial in modern ignition systems. For high-mileage engines, the enhanced durability of double platinum plugs helps maintain a precise spark gap for longer. This consistent performance can help compensate for some inefficiencies that develop in an older engine.
What To Consider for Your High-Mileage Car
Your owner's manual will specify the plug your car was designed to use. You can often upgrade, but you should never downgrade.
If your older vehicle originally came with copper plugs, an upgrade to platinum or iridium can offer tangible benefits. The longer life and more consistent performance of these plugs are well-suited to the demands of a high-mileage engine. The improved ignition efficiency can lead to better fuel economy and smoother engine operation.
The Role of Heat Range
The heat range of a spark plug refers to its ability to dissipate heat. A "hot" plug has a longer insulator nose and retains more heat, which helps burn off carbon deposits. A "cold" plug has a shorter insulator nose and dissipates heat more quickly, which is ideal for high-performance engines.
If your high-mileage engine has issues with oil fouling, a slightly hotter spark plug might help keep the electrodes clean. It's best to talk to a trusted mechanic before changing the heat range.
Your Best Bet: Iridium and Double Platinum
For most high-mileage cars, iridium spark plugs are the top tier. Their exceptional durability and efficient spark delivery provide the consistent ignition older engines need. They resist fouling well, which reduces maintenance and helps the engine run at its best. Car spark plugs made of iridium can justify their higher initial cost through longevity and fuel savings.
Double platinum plugs are another solid choice. They offer a good balance of longevity and performance at a more moderate price point than iridium. If your car was originally equipped with platinum plugs, double platinum is a sensible upgrade that will stand up to the conditions in your high-mileage engine.
How To Get the Most from Your Spark Plugs
Once you have the best spark plugs for your high-mileage car, proper installation is next. The spark plug gap must be set correctly, and the plugs need to be torqued to the manufacturer's specifications. An incorrect gap or torque can lead to poor performance or even engine damage.
Regularly check your spark plugs for signs of wear or fouling. The condition of your old plugs can provide valuable information about your engine’s health. For example, oily deposits may indicate worn piston rings, while a white, blistered appearance can point to an engine running too lean.
Final Thoughts on Your Ignition System
Just because your car has a lot of miles on the odometer doesn't mean its best days are behind it. Proper maintenance with quality parts can keep your vehicle running reliably. Selecting the correct spark plug is a crucial part of this upkeep. For older engines, the longevity and efficiency of iridium and double platinum spark plugs can make a significant difference, ensuring your high-mileage car performs at its best.
When you're ready to make a choice, consider E3 Spark Plugs. Our DiamondFIRE electrode technology is designed to create a more efficient and complete burn, which can improve power and fuel economy. Explore our catalog to find the right fit for your vehicle and keep your car on the road.
