the 2017 Hyundai Sonata spark plugs are original stock when new - despite age , the Hyundai just turned 50K miles and I only use top tier fuel , gets a bottle of Techron twice per year and I keep the PCV valve clean . Driving is mixed , mostly large city suburban driving and some highway driving and work is a 40 minute drive one way . Fairly typical driving pattern . Supposedly , stock iridium spark plugs can go 100K miles but I am thinking at 60K + miles and 7 years I may wish to change early . My concern is if I wait too long there may be a negative impact to the coils (which are more costly to replace) .... Your thoughts and experiences if replacing spark plugs a little earlier is better than waiting the full 100K mile mark ?
When To Change Stock Spark Plugs ?
- Thread starter ChrisD46
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iridium spark plugs really can go 100k 
I changed the plugs on my Honda Civic at 75,000 miles and it took me about 1/2 hour tops. My Corvette plugs on my 2005 were more difficult and I sold it with 82,000 miles with the original plugs. If they are very difficult to replace I go as long as I can or about 100,000 or more if I still have the vehicle. I usually do not keep them that long though except for my Civic which has 135,000 and showing no signs of wear on the engine or transmission.
Spark plugs do not have a time expiration date. You change them by miles regardless of age.
There are exceptions of course, like if they are hard to get to or require a lot of stuff to be taken apart. So if you are already in there for something else, may as well change them even if they didn’t hit the mileage yet.
There are exceptions of course, like if they are hard to get to or require a lot of stuff to be taken apart. So if you are already in there for something else, may as well change them even if they didn’t hit the mileage yet.
1/2 ton trucks or any gasoline truck really that tows a lot tend to be harder on them as they fire more often than in a sedan due to higher RPM over the amount of miles driven.
It has been my experience that in a well maintained car, OEM quality spark plugs will easily make it to the recommended change interval.
Some cars are harder on spark plugs than others, and the service manual will reflect that. My Outback and E350 both call for changing plugs at 60k miles. But I have had other cars with service manuals that called for spark plug replacement at 130k miles. And the plugs still met gap when replaced at 130k miles.
Some cars are harder on spark plugs than others, and the service manual will reflect that. My Outback and E350 both call for changing plugs at 60k miles. But I have had other cars with service manuals that called for spark plug replacement at 130k miles. And the plugs still met gap when replaced at 130k miles.
That is all factored into the service recommendation. If the engine is running as it should, no misfiring, oil consumption, overheating, etc. the plugs will do whatever interval is specified.
Shel_B
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My first car with factory iridium plugs went more than 120,000 miles. At 120,000 or so I examined the plugs, and by my estimation and the opinion of a trusted tech, the plugs had quite a bit of life left.
The Camry had factory iridium plugs and they were changed at about 90,000 miles. They could have gone a bit longer but I wanted fresh plugs as part of the prep for a multi-thousand mile road trip I was planning.
If you feel a need or desire to swap the plugs, go ahead and do it. It's just a few dollars and if it makes you feel better/more secure, it's money well spent. That said, your plugs are probably just fine.
The Camry had factory iridium plugs and they were changed at about 90,000 miles. They could have gone a bit longer but I wanted fresh plugs as part of the prep for a multi-thousand mile road trip I was planning.
If you feel a need or desire to swap the plugs, go ahead and do it. It's just a few dollars and if it makes you feel better/more secure, it's money well spent. That said, your plugs are probably just fine.
AZjeff
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Exactly. And if a coil pack should go bad during OP's ownership...
Changing plugs every 7 years is less expensive than short OCIs.
Iridium plugs can go 100K miles unless abused or defective.
They can be abused by using poor quality fuel that causes pre-ignition.
In most cases, these plugs can go forever, until they fail due to gas leakage. The recommendation to change them is to get them replaced before any such leakage develops. Some manufacturers recommend as little as 60K miles. I don't ever recall seeing a recommendation of over 100K.
I would stick to NGK or Nippondensos for replacements.
They can be abused by using poor quality fuel that causes pre-ignition.
In most cases, these plugs can go forever, until they fail due to gas leakage. The recommendation to change them is to get them replaced before any such leakage develops. Some manufacturers recommend as little as 60K miles. I don't ever recall seeing a recommendation of over 100K.
I would stick to NGK or Nippondensos for replacements.
Shel_B
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+1 on the recommendation
Gas leakage ? That's a new a issue
the R stands for Resistor
Changed the factory Iridium plugs in my Infiniti at 115k miles and only did it, what's the phrase used here, "it's cheap insurance". I mean, by the maintenance schedule they were due, past due actually. Gap is 0.043 and (6) of the plugs were 0.043-0.044 or so while two were around 0.046. Car was running just fine and afterwards, I couldn't tell any difference, nor did fuel economy change.
I can usually tell the gap has gotten too large and time to replace, when in the winter, the depressed battery voltage due to the low temperature, causes the spark to be weaker and it takes longer to start.
Otherwise I wouldn't replace platinum or better, before 75K mi without a known issue like burning oil that fouls them. After 75K mi it is a matter of convenience when doing something else that makes that easier, (depending on engine design) or about 10 years for the first swap... I don't like to leave plugs in longer than 10 in case they get hard to remove.
After that first ~100K spark plug replacement interval, for 3rd set of plugs, I drop down to at least 50K change when convenient, or about 75K just to get it done. Also depends on how much work is needed. It's much easier on some engines/vehicles than others.
The other school of thought is, if it ain't broke, don't fix it. BUT, considering all the inherent costs in operating a vehicle, having to replace a coil (because stressed from too large a spark gap) isn't all that expensive. Weigh it against all the many other preventative maintenance costs trying to cover all "just in case" failures, and what hardship it would cause if there was a failure taking a vehicle out of commission for up to a few days. For some frail owners, any amount of money or effort to mitigate future problems is worth it if being stranded poses a medical risk.
If it's just a hobby to be ahead of the curve like many on BITOG make it, replace the spark plugs instead of losing sleep over it. Don't look at it as an expense you could avoid but instead an expense you will have to pay anyway (unless soon selling the vehicle) so the cost per year for the life of the plugs, wasn't much different.
Otherwise I wouldn't replace platinum or better, before 75K mi without a known issue like burning oil that fouls them. After 75K mi it is a matter of convenience when doing something else that makes that easier, (depending on engine design) or about 10 years for the first swap... I don't like to leave plugs in longer than 10 in case they get hard to remove.
After that first ~100K spark plug replacement interval, for 3rd set of plugs, I drop down to at least 50K change when convenient, or about 75K just to get it done. Also depends on how much work is needed. It's much easier on some engines/vehicles than others.
The other school of thought is, if it ain't broke, don't fix it.
BUT, considering all the inherent costs in operating a vehicle, having to replace a coil (because stressed from too large a spark gap) isn't all that expensive. Weigh it against all the many other preventative maintenance costs trying to cover all "just in case" failures, and what hardship it would cause if there was a failure taking a vehicle out of commission for up to a few days. For some frail owners, any amount of money or effort to mitigate future problems is worth it if being stranded poses a medical risk.If it's just a hobby to be ahead of the curve like many on BITOG make it, replace the spark plugs instead of losing sleep over it. Don't look at it as an expense you could avoid but instead an expense you will have to pay anyway (unless soon selling the vehicle) so the cost per year for the life of the plugs, wasn't much different.
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Usually I'd see that in the part number vs a stand alone "R" on the ceramic body.
I figured it was Ruthenium, or Rhodium, but sure resistor makes sense as well.
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