Is spark plug change at 100,000 miles recommended service if having no issues?
As with any delayed maintenance, it’s a gamble. You might get away with it or the car can fail at the worst possible time.
If the owners manual calls for it, I’d do it. Use only the plugs recommended by the carmaker.
My 97 Accord has the original plugs at 220,000 miles.
If the Check Engine light comes on for a misfire code, then I’ll change them.
Some people go to the dentist once a year whether they have an issue or not. Some people only go when they have a toothache.
Some people change their furnace filter once a year. Some people wait until the heat quits working properly.
Some people restart and update their computer once a week. Others wait until it doesn’t run anymore.
I’ll never understand why people don’t do basic routine maintenance on schedule for their car. But I don’t go to the dentist regularly. Go figure.
The plugs are extremely easy to replace and they are not too expensive. Toyota’s are fussy about plugs, do not use an equivalent. I ended up buying Denso plugs from the dealer at a fair price.
Maintenance is a lot cheaper than an unexpected breakdown and repair.
Plugs can develop subtle misfires that won’t set a code or turn on the CEL. I think it was db4690 that alluded to this a few days ago and it’s something I’ve also brought up a number of times.
Subtle misfires may not be noticeable to the driver but if one was to watch an oscilloscope pattern they could be seen.
I would be too curious to see what they looked like at 150000 to leave them in there.
However, I have a 1972 8 hp Airens Snowblower that I bought in 1990. I changed the spark plug once since 1990. I will change it again if it gets hard starting. It has never been to a shop since I got it.
I had the plugs replaced in my 2009 at 110k and one of them was past due at that point. 100k seems prudent.
Many years ago, I made an offhand remark at work about needing to stop at Home Depot to pick up a new furnace filter. One of the women with whom I worked seemed intrigued, and asked, “How often do you need to change it?”. When I told her that I change mine every 4 months, she blanched and asked if all furnaces have a filter.
So, after work, I first stopped at her house, opened up her forced air furnace, and found the most incredibly HUGE pile of dust bunnies on her furnace filter. It turned out that she had lived there for 7 years, and had never changed it.
So, I went to Home Depot, bought the correct filter for her furnace and for mine, returned to her house, and replaced the filter. Miraculously, her furnace was still running properly, even after that theoretically clogged filter.
Some people just seem to luck-out.
The air might have been going around the filter rather than through it. We have to be careful when replacing HEPA filters at work. They are basically a long piece of pleated paper in a metal box. As you might expect, it takes a lot of pressure to force air through the paper. Air is much more likely to go through rips in the filter or around the filter box if it isn’t seated right.