I just installed a set of E3's in my 07 Hemi with 60K, as well as a set in my 06 Grand Cherokee Limited 30K-yes I love the Hemi. Buying 32 spark plugs was a first. I got a good deal on the plugs and so far working well with no problems at all. I do have to say ya'll are making me nervous though. No real difference felt in the Ram, but the Jeep goes like a scawled cat!

 

I have the E3s in my truck, ATV and one Lawnmower. All three run great.
The truck gets better mileage but not a lot. The ATV starts and runs stronger than before. The Mower has not needed a new plug in 3 years and starts and runs fine.. Not sure where or why all the negativity over these plugs. They seem to work great for me..

 

One negative thing is the cost. Geez.....close to $100 to get what back out of them? Thats why I can runt them. Now if someone gave them to me and let me try them and IF they did get substantially better MPG, then I would pay for them. But I cant cough up $100 +/- for some plugs and they might work better and they might not.

Ive got OEM coppers in mine and have had zero idle or high RPM issues and they are 1.76 each last time I bought some.

Not knocking E3's but just cannot justify the cost. Im not that curious.