Replacing spark plugs is routine maintenance you shouldn’t ignore. The quality of your spark plugs directly impacts the health of your engine. As spark plugs age, they stop firing reliably. Once you lose one, you’ll notice a big reduction in power.
How often you should change your spark plugs will depend on the make and model of your car. You can expect it to be around 30,000-50,000 miles, at least. Knowing how to change spark plugs is a valuable skill. This simple maintenance can turn into an expensive affair at the mechanics.
Don’t overpay for spark plugs or 30 minutes of light work. Follow our guide on how to install spark plugs and you’ll keep your car running strong and long.
Tools and Preparation
Before we do anything, you’ll need to purchase the correct spark plugs. Consult your owner’s manual for the exact type of spark plug. Never downgrade to a cheaper spark plug to save money. For example, if your car needs a platinum plug, don’t replace it with a copper plug.
Depending on your engine type, the only tools you really need is a wrench, a spark plug socket, and some dielectric grease. If your spark plugs sit low or behind the engine block, you may need some extenders or socket adapters. You can get these parts online at a discount.
Before you start removing the old spark plugs, use a can of air to blow away any debris surrounding the plugs’ surfaces. Continue this into the next step.
Removing the Old
This is a good opportunity to check the spark plug lines to see if they are bad, too. If they look weathered, frayed, or show damage, go for a new set. They aren’t expensive and are “plug and play” as far as installation goes.
These are car maintenance tasks that you don’t need a professional to avoid messing things up. It’s a no-brainer when it comes to changing spark plugs.
You should be able to pull out the spark plug cables at the cap base with little trouble. Don’t tug on the cable itself if you don’t plan on replacing them. Once it’s out, you can take your socket wrench and start unscrewing the spark plug.
Wait, before you pull the first one out, take a vacuum or can of compressed air and go over the hole first. Make sure there is no small debris that fell inside. You don’t want anything to fall below into the engine.
Are They Bad or Still Good?
Spark plugs don’t have an automatic timer for when they expire. They gradually degrade over time, which can vary. Look to see if there are any cracks in the white ceramic end of the spark plug. Discoloration is fine, but there should be no lines in the ceramic.
Rust anywhere is bad, of course. Usually, the lug nut will collect rust or mineral deposits. You should replace them as it’s just not worth trying to clean it off.
Finally, take a look at the igniter. Is the gap wider than it should be? Is there a build-up of impurities on the far end? These are all signs of a bad spark plug that isn’t firing 100%. Impurities can be sanded off sometimes, but you might not get enough of them off to stop the plug from misfiring.
Prepping the New
After you’ve received your replacement spark plugs, it’s time to inspect them. Are they the correct type? Copper, Platinum, or Double Platinum are the standard types. Iridium spark plugs are more durable, but also more expensive.
Next, take a look at the gap size specified in your car manual. Make sure the ones you bought are the same size. You can buy a cheap spark plug gap measurement tool to check all the plugs to make sure. Spark plugs come pre-sized, but you can never be too careful.
Stay within the manufacturer’s parameters. Too wide of a gap and you’ll get misfires, too small and the spark could be too weak to ignite the cylinder.
Next, take some dielectric grease and apply it to the ceramic end of the spark plug. Be careful to not get any on the threading side. This can gunk it up and make it difficult to remove later. While you’re at it, take some of that grease and lube up the ends of the spark plug cables.
Time to Change Spark Plugs
Now that everything is prepared, it’s time to put the new plugs into place. It might seem very obvious (put the new ones in and turn counter-clockwise, duh). That’s how mistakes are made, however, so do this methodically.
Work on one replacement at a time, placing the new plug inside and putting the cable back in. Watch how much you’re tightening your new plugs, though. Too much and you could strip the threads, too little and it could vibrate loose.
Investing in a torque wrench can remove the guesswork. This will allow you to set how much pressure you want on the turn, so you can’t go overboard. We recommend about 15 pounds of pressure with a slight twist after you can no longer turn it by hand.
If you follow along with this guide, there’s no reason why you shouldn’t be able to change spark plugs for less than $100. Yes, there are some engines where accessing the plugs isn’t as easy or straight-forward. No, that doesn’t mean you can’t do it by yourself, you just need to finesse it.
We understand that looking under that hood can be intimidating for someone with no experience. Don’t let that stop you from taking problems in your own hands or preventing them altogether. Regular maintenance and replacement of parts can add 100’s of thousands of miles to your car.
Check out more guides like this one at our automotive maintenance blog. We’ll share industry secrets, give you unbiased reviews on parts, and more. Our vehicles are like extended members of the family. Help them stay healthy and your vehicle will pay you back many times over.