spark plugs

When and why to replace spark plugs

In Vehicle Maintenance by HomeTowne Auto Repair & Tire

Drivers who have had the misfortune of unsuccessfully starting their vehicle tend to consider a few common problems: a dead battery, a bad starter, or the alternator needs to be replaced.

However, there are other possible culprits that can be overlooked, such as bad spark plugs. These components help turn on a vehicle by igniting fuel in the cylinder head.

Changing them is an important part of car maintenance.

Not only does replacing spark plugs allow you to start your vehicle, it also prevents bigger problems and is one thing you can do to get better gas mileage.

How often to replace spark plugs

As the automotive industry has evolved, the amount of time certain components can last has increased. At one point, new spark plugs were needed every 30,000 miles. Now, they can make it twice that distance or longer.

Depending on the vehicle and what the manufacturer suggests, spark plugs could last anywhere from 60,000 to 105,000 miles.

Other than time, they may fail because of various circumstances – carbon buildup, oil getting into the combustion chamber, and overheating of the spark plug tip.

As it comes time to change out old spark plugs, there are some things you should keep in mind. 

First of all, it’s a good idea to go with those that are high quality and Original Equipment (O.E.) manufacturer specific. This is because some part producers specialize in certain makes. Also, the type of material that a spark plug is made out of can play a role in its lifespan.

Bad spark plug symptoms

Time isn’t the only way to determine if these components are ready to be replaced. Various problems can be the marking of a bad spark plug. 

In addition to having trouble starting a car, you may notice other indicators. Some signs include misfires, the check engine light turning on, and a vehicle running rough when it’s idle.

Misfires happen if fuel doesn’t ignite the way it should. They may be accompanied by the check engine light coming on and shuddering.

An important safety note: It’s safe to use a vehicle if the check engine light is on steadily. However, if it’s flashing, you should pull over or avoid driving it.

The importance of changing spark plugs

The type of metal the tip is made out of – whether it’s platinum or iridium – will determine how long the spark plug lasts. Every time it sparks, the metal wears down a bit.

For one vehicle we worked on, the spark plugs hadn’t been changed for 130,000 or 140,000 miles. Because the gap was so large, it ruined the ignition coil.

One reason you should replace them on a mileage-based timeframe is because the electronics in the vehicle are so much better and can produce a higher spark to jump that gap. What you don’t notice is how it affects a catalytic converter overtime. The computer is trying to compensate for the gap and make everything run correctly. 

If you need to change the spark plugs at 60,000 or 90,000 miles and you replace them on time, your vehicle will run better and experience less wear, allowing the subsystems to last longer. Some vehicles – even a lot of performance vehicles – may use regular, copper spark plugs that need to be changed every 30,000 to 50,000 miles.

So, you really need to look at your owner’s manual to find out what frequency you need to be on.

Tip: Depending on the manufacturer, you may want to change the components earlier than normal. If it’s a lifetime spark plug or one that can last up to 100,000 miles, it may be a good idea to replace them at 50,000 or 60,000 miles. Based on the metal the cylinder head and spark plugs consist of, they could seize inside the cylinder head and you won’t be able to get them out. If you take them out earlier – even if they aren’t worn out – you’ll be able to replace them again in another 50,000 miles, rather than them getting stuck and costing you more money.

HomeTowne Auto Repair & Tire is an authorized Michelin and BFGoodrich tire dealer located in Woodbridge, Virginia. Automotive repair services are performed on all makes and models, including oil changes, brakes, alignments, inspections, and computer engine diagnostics.