So just passed 217,000 miles on my '99 GS400 and still have the OEM plugs. Indy looked at them at 200,000 miles and said they were fine. In 17 years the car has never had a problem starting, starts on first turn every time. My only concern is, should I change them just as a precaution? I'm heading in for my second TB/WP change at 220,000 and could change them then, or wait since they are not causing me an issue.

 

OEM from factory, 217,000 on them? I say replace them, keep the originals and put them up for auction at a museum...

ok honestly. I say replace them (since they should be changed at no later than 20,000). Keep the originals. If the car runs worse, put the originals back in and keep rollin... For just a few bucks, replacing them is worth it. At the same time, replace the wires too; and if you have the extra money, replace the coils as well... I would bet you'll see a difference in performance and at the very least, fuel economy. Just because they look fine, doesnt mean they're working at 100%

 

Haha, thanks. I bet it would make a big difference doing the wires and coils at the same time. I'm all for more performance

 

While you're at it... Add a supercharger

 

That's pretty cool. The long life ones are rated at 100k miles. Still, I would put new ones in for peace of mind. While they still work fine, they may not be at 100% efficiency. Considering the low cost, it should be done.

 

I changed mine just for peace of mind

that said I've seen oem denso plugs on Corollas with over 350,000km on them and they seemed to work like new, so you're probably fine

 

I just change them every 90K when I do the timing belt.

 

How long is too long for spark plugs?

217,000

 

Just wanted to provide an update, finally changed out the original OEM spark plugs at 224,318 miles. Had a second timing belt / water pump change a few months ago so all service is up-to-date.

 

Were they difficult to get out?

We had a 1997 Ford truck that had 127k miles and original plugs and several of them broke off in the head while we were trying to get them out. I have no desire to ever go through that again.

 

Nope not at all, I've had my Indy check them a few times before. I just changed them as a precaution. I figured after 18 years it was time lol.

 

20,000 huh

 

Sure, some of them are built to last upwards of 60k but since they're (relatively) cheap I always do mine every 30k regardless.

 

Yeah I'll do that as well. The car seems to run a lot smoother with the new plugs in.

 

if your ever going to change the spark plugs minds well change out the valve cover gasket and vice versa