spacecraft

I just had the spark plugs replaced on my RX400h.
The job was done by my usual (non-official) shop, which I've always been happy with in the past.
In this occasion, they also did a good job as far as I can tell, and the car runs just fine.

But when they showed me the old plugs, which I asked them to keep because I was curious to see how they looked like, they gave me three NGK (IFR6A11) and three Denso (SK20R11).
They told me that each cylinder bank had a different brand fitted, and asked me if I possibly replaced only the front plugs in the past, which are obviously much easier to access.
But I never did anything like that, and while I can't be positive about the first owner, the car only had clocked 30k miles when I bought it.

This made me wonder if by chance they saved themselves the hassle to replace the rear bank plugs, and not having handy 3 plugs identical to the front ones, they showed me some others...
Not that I have any reasons to doubt of their honesty, but I find it hard to believe that the car came from the factory with different plugs on each cylinder bank.
Or is that a possibility? Did you folks ever heard of this happening?

BTW, different brand aside, all the six plugs looked in pretty good conditions, clean and with a nicely normal colour.
Practically impossible to separate the Denso from the NGK, looking only at the electrodes.

Thanks in advance for your views.

iMSQ

Nobody will use a "mix" of brands at assembly line.
How old was the car when you bought it?

spacecraft

Less than 4 years old, but I'm pretty sure that the 30k mileage was genuine, 'cause it was in as new conditions overall.
And I can't think of any reason why someone should have fiddled with plugs at that sort of mileage...

LewisLou

I know toyota used two types of spark plugs in some 4th gen 4Runners

DennisMik

Other than this being a curious thing, both of those spark plugs are the models made for your car. I wouldn't spend too much time dwelling on it.

spacecraft

Yup, I did check that both models were of the right specs, that's not what I'm worried about.
My reason for dwelling on it (only up to a point, anyway...) is the doubt that my mechanic might have pulled my leg.
Also because, if that would be the case, on top of having paid for a work not properly done, I would still have 3 old plugs back there, where even just checking them is a royal PITA...

Felix

BTW the 3mz is a little easier then a 2gr to deal w/ the bank one plugs.......