Just finished spark plug change...they were...

Right, that still does not tell you to use 3 of each on each bank. It says either or. There IS a reason Toyota does this during assy. and then tells you to use either or for replacement If it was something that was NEEDED then we would do the same at 30K.

 

Don't argue with the man he has 31,196 post, oh wait make it 31,197 hold ont 198 (dang it Chris stop posting so much!)

 

I had to get on ths forum and find out why I found 3 different factory installed plugs in my truck. I was thinking it was a mistake or something. But after reading everyone else's reply, I think I know why they do it.

Toyota is gathering data on the plugs and comparing the findings. When the dealership changes the plugs they collect a ton of data: mileage of vehicle, the final gap on the plugs and they keep the plugs.

It is a perfect test. Toyota has leading edge manufacturing techniques. It makes perfect sense to compare plugs at 30K miles after real world testing.

 

Couple of things that also come to mind and make me think.

First thought, they quit putting 100k plugs in the vehicle because it costs their dealerships lots of service work. Most people don't have the tools nor skills to change their own plugs. (I hear that dealerships make more money from service than sales. I don't know that to be true but it sounds good.) Back to my point, assume a 200k life on a Toyota with 30K mile plugs and there are 6 service trips for plug changes, with 100K mile plugs you only need to get 1 service trip for a plug change. These plugs earn the dealership 5 service trips.

My next thought, in college we learned how to design equipment to meet a specific lifecycle. Those classes are the first thing I thought of when I realized that Toyota puts differents plugs in every truck. Sounds like they are looking to find that 30k mile plug.

When you connect the two points together it seems to make a lot of sense to me. Especially knowing that there are books based on Toyota being a World Class manufacturing model. They do everything for a reason.

Side note, when I usually change plugs, I normally inspect the condition and throw it in the trash. But for some reason, I laid these out on the bench in order and then I noticed three different models. I inspected their gaps and checked their resistance. Two models were consistent but one model had lower resistance and a larger gap. I don't know what to do with the information but I did observe that.

When I noticed the different models, I was initially upset. I would not expect that Toyota would make such a mistake. How could they screw that up? So I came here. Since they do it to everyone they must have a very specific reason.

 

Sorry new toyota, but I have a thought, are these on distibuer less systems? or wired?
my thought is if they have ignition wires, they might be compensating for restance in the wires.