spark plugs - why 30k?

Not getting close to my first plug change yet but I was wondering why in this day of 100k tune ups Toyota specs a 30k interval for spark plugs in our 4.0Ls. Even my old 1994 Camaro had a 100k interval (with platinums). I changed em out at 50k when they still looked fine and then ran non-plats in it for another 50k and they still looked great, too. So the longer intervals don't seem entirely due to using platinums. Are there automotive engineers here who can tell us what about these motors mandates more frequent plug changes? Spark voltage, combustion temps, oiling issues, what???? All this said, it doesn't look particulary hard to do the plugs.

 

I don't understand either. I changed mine at 45k miles and they still looked good.

Gap was .40 on the old plugs.

 

Not interested in a debate about how often and why people change their plugs. Since this is different from just about any vehicle I have seen for awhile I am just curious if anyone knows of an engineering design basis for the Toyota 30k spec. If no one knows, no biggie.

 

The standard truck has a 30k mile plug replacement. If you swap them out the the platnium plugs they sell those have a 100k mile replacement plan. I can only imagine that most people would not go in a regap the plug after 30k miles and if they did maybe you can accomplish the same thing, higher efficiency. Of course if you are taking the effort to pull the plug out, why not spend the 5 bucks and put a new one in rather than the old one... Who knows... might be worth a shot, or it could just be a waste... I Think the answer to this mystery is in the same lock box that the JFK question is in...

 

What he said

 

Sometimes we don't get what we want when we post online, do we? Try a better tone and maybe you'll get more help. Luckily, Chris is a nicer guy than I and chooses to assist you.

 

That was a nice tone. It is always a challenge to get "what you want" on a forum and it is likewise a challenge to refocus a thread w/o sounding like a dick. But if you aren't clear about it attempts to refocus rarely are successful... and we get another thread with 50 opinions on when to change spark plugs. Gack! BTW, this isn't a thread about help. Just trying to understand Toyota's engineering approach. Chris's points make some sense. It is possible that the copper plugs for whatever reason dyno a couple HP higher. But I don't believe the ignition puts out more voltage that other modern HEI systems that use plats. My gut feeling is that since it is relatively easy to change plugs the benefits of the potential modest HP gain and chance to read the plugs periodically outweigh the benefit of a longer tune up interval. And maybe make some additional revenue for dealer service depts? Probably splitting hairs on the benefit tradeoffs though....

 

the hundred thousand mile tune up was just marketing i was a tech at a caddy dealership for about 7 years and a independent shop for about 6 years i know on my old 99sr5 i changed them at about 45k and it made a difference no fluid,spark plugs,or filters should be left on your truck for 100k it's not good practice prementive maintenance is the best way to keep your truck going

 

Sounds good Chris, let us know. I are an enguneer, too, just not the right kind. Never had a course in engine design. Another thought that occurred is that perhaps they factor in the possibility of extra hard duty like towing in deciding on spark plug choice and service interval. Who knows what lurks in the minds of Toyota engineers?

 

My truck currently has 40K on it and I'm looking to replace the spark plugs as well. The funny thing is I asked the dealer to do this when I had it in for the 30K and they said it wasn't necessary. Checking the manual says otherwise, but I took their word at face value. In any event, which brand are others buying to replace their OEM plugs or are most just going to the dealer? The manual lists part number which I'm sure matches up to an after market plug. I presume we should use like for like here and not install platinum or irradium plugs?

 

30k - copper based plugs......100k - iridiums.

 

I generically replace them every 50k and even so, they still look pretty good. My brother who used and abused his didn't change his until 150,000. There wasn't much left of the electrodes needless to say...

 

I would be surprised your brother didn't notice a difference in performance long before 150K?

 

Like Chris said spark plugs are cheap and not hard to change on our engines. I did mine in an hour and will have to change them again soon. I'm at 51k now.
As far as the reasoning behind the interval I have to say they have a method to the madness. Those engines that specify 100k intervals may take years or a decade before they reach that point.
I have seen firsthand plugs seized in heads due to lengthy intervals. Especially on aluminum heads. This may have something to do with Toyota's 30k interval.

 

I had a 2002 Accord with 100,000 mile plugs, but I changed them at 60,000 miles and noticed an improvement in performance. I plan on changing the plugs in my 2.7 Tacoma at 50,000. If the 4.0 is using copper plugs, I would absolutley change them a 30,000. JMO.

 

Don't know the technical reasons behind the 30000 change, however for the folks using NGK or Bosch Iridium plugs change them at 30000. I've noticed that the center electrode will erode with time and open up the gap significantly. It's easy to spot, usually the center electrode will start out thick at the base and taper to a finer point. The plugs I've pulled the taper is gone. I didn't affect day to day performance but it's not optimum.

 

Do not replace the standard plugs in a Tacoma with platinum or otherwise. Longevity is the least of the concern when it comes to the plugs on a Tacoma. As Chris mentioned the standard resistor plugs put out a different heat range and spark. The vehicle is designed for this plug to do the job. Using a differnt type of plug affects more than just the spark. Over the long run damge to the cylinder walls can occur as well and certainly a lack of performance. When initally using a different type of plug you may not feel it but will see a difference in fuel economy and also the potential of a higher emmisions rating. Using a colder plug such as an irridium or platinum is going to cause a wash out inside of the cylinder since it is not burning as hot and this translates into poor fuel economy and performance. I beleive that Toyota uses the resistor type plugs for emmissions reasons more so than anything else.