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And dont worry if the springs arent centered and dropped into the holes in the plug boots on the coil.
The plug top sticks through that shoulder and contacts the spring regardless.
 

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I just switched to these yesterday. The sku is FR7BHX-S so they are a colder plug than the stock ones. When I bought them over the weekend at RockAuto they were $7.50 a plug; they are asking $8.12 a plug now. CarID has them for $8.50 a plug.

They seem to to help in the same way as the copper plugs that others have tried. Gapped them as close to 0.028 (NGK says they are supposed to be gapped to 0.027 for the 2011 Cruze) as I could: No more hesitation at higher RPMs, slow acceleration is gone - even after sitting at a stop light for a couple minutes, and running the ac at the full speed of 4 produces a vibration along the lines of a purring cat (I’ll swap my hvac module and control panel over to the ones I pulled from a 2014 at some point to see how they handle the full speed of 6).

I’m not on here much these days, but I’ll try to remember to give a 1 month report on the plugs.
Has it been a month already? Sheesh.

So far I have been fairly impressed with the new ruthenium plugs I installed. Quick starting even after sitting overnight, idle is extremely smooth at all 4 AC speeds (when set at 4 the vehicle idle starts to be noticeable but nothing worse than a minor growl - similar to an unhappy puppy) & a couple of times at gas stations I actually thought that I hadn't turned my car back on when I was not using the AC. Acceleration from a stop, especially at long stop lights, is smooth and powerful with no indications of heat soak affecting the plugs. When accelerating on inclines I do not feel any kind of lag or delay - both on or off cruise control. I haven't done any official temperature measurements, but I can definitely state that the hood of my car is a lot cooler to the touch after long drives to and from work and I haven't heard my cooling fan running in "fighter jet" mode since I switched.

Unfortunately for me, when I'm driving I have to deal with more city driving than highway driving so my calculated average mpgs are low - but they have improved with the new plugs - going from 24.7 to 26.5... even with the ac on (usually set between 1 and 2. I haven't used 3 & 4 as they are overkill in this cooler than usual and very much less humid St Louis summer).

Of course, as usual, ymmv depending on the condition of your vehicle, type of use, maintenance patterns, etc.
 

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Has it been a month already? Sheesh.

So far I have been fairly impressed with the new ruthenium plugs I installed. Quick starting even after sitting overnight, idle is extremely smooth at all 4 AC speeds (when set at 4 the vehicle idle starts to be noticeable but nothing worse than a minor growl - similar to an unhappy puppy) & a couple of times at gas stations I actually thought that I hadn't turned my car back on when I was not using the AC. Acceleration from a stop, especially at long stop lights, is smooth and powerful with no indications of heat soak affecting the plugs. When accelerating on inclines I do not feel any kind of lag or delay - both on or off cruise control. I haven't done any official temperature measurements, but I can definitely state that the hood of my car is a lot cooler to the touch after long drives to and from work and I haven't heard my cooling fan running in "fighter jet" mode since I switched.

Unfortunately for me, when I'm driving I have to deal with more city driving than highway driving so my calculated average mpgs are low - but they have improved with the new plugs - going from 24.7 to 26.5... even with the ac on (usually set between 1 and 2. I haven't used 3 & 4 as they are overkill in this cooler than usual and very much less humid St Louis summer).

Of course, as usual, ymmv depending on the condition of your vehicle, type of use, maintenance patterns, etc.
This sounds quite promising! Interested to see how long they hold their gap - the main issue with the BKR series.

Sent from my SM-G950U using Tapatalk
 

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Has it been a month already? Sheesh.

So far I have been fairly impressed with the new ruthenium plugs I installed. Quick starting even after sitting overnight, idle is extremely smooth at all 4 AC speeds (when set at 4 the vehicle idle starts to be noticeable but nothing worse than a minor growl - similar to an unhappy puppy) & a couple of times at gas stations I actually thought that I hadn't turned my car back on when I was not using the AC. Acceleration from a stop, especially at long stop lights, is smooth and powerful with no indications of heat soak affecting the plugs. When accelerating on inclines I do not feel any kind of lag or delay - both on or off cruise control. I haven't done any official temperature measurements, but I can definitely state that the hood of my car is a lot cooler to the touch after long drives to and from work and I haven't heard my cooling fan running in "fighter jet" mode since I switched.

Unfortunately for me, when I'm driving I have to deal with more city driving than highway driving so my calculated average mpgs are low - but they have improved with the new plugs - going from 24.7 to 26.5... even with the ac on (usually set between 1 and 2. I haven't used 3 & 4 as they are overkill in this cooler than usual and very much less humid St Louis summer).

Of course, as usual, ymmv depending on the condition of your vehicle, type of use, maintenance patterns, etc.
Since the cooler, less humid weather you are experiencing is causing you to not demand as much from your a/c system, by not needing higher blower speeds, your a/c compressor is certainly spending less time engaged during cycling.
Your engine cooling fan spending less time on high is also likely the result of the same conditions.
So that may also explain a good portion of your fuel economy gains...
The NGK "7" heat range is the stock heat range for these engines.
I believe some of the early models called for a "6" range, but that was changed on later models, and that the replacements for the older engines were revised to use the 7 as well.
An "8" heat range plug would actually be one step colder than stock.
And short of your previous plugs being worn out or defective somehow, I just cant imagine two sets of plugs with similar heat range and gap having such drastic differences in vehicle behavior.
Dont get me wrong, not trying to bust your chops, it's just that I've been down this road more than a few times myself, and short of something being wrong with the old plugs, I've never seen a different set of plugs provide any meaningful gains.
 

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This sounds quite promising! Interested to see how long they hold their gap - the main issue with the BKR series.

Sent from my SM-G950U using Tapatalk
So far they are holding the gap a lot better than the coppers recommended in the 1st post did. I replaced both the coil pack and my plugs in early may after a major coolant hose blowout sprayed up under the cover and into the plug wells. Tried the BKR7E-4644s which I personally gapped at 0.028 as a low cost trial to see how they did. By the end of July I was having problems with hesitation and poor acceleration. When I took them out to put in the ruthenium plugs I checked the gap and three were at 0.034 and the 4th one was at 0.036.
 

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So far they are holding the gap a lot better than the coppers recommended in the 1st post did. I replaced both the coil pack and my plugs in early may after a major coolant hose blowout sprayed up under the cover and into the plug wells. Tried the BKR7E-4644s which I personally gapped at 0.028 as a low cost trial to see how they did. By the end of July I was having problems with hesitation and poor acceleration. When I took them out to put in the ruthenium plugs I checked the gap and three were at 0.034 and the 4th one was at 0.036.
How many miles did you accumulate on the BKR7Es?
I'm currently running those, but I've only had them in for about a thousand miles or so.
I have a set of BKR8EIX ready to install. I may just go ahead and swap them in.
Im curious to see if they help out on the slight amount of knock retard I'm getting on 89 octane fuel.
On 93 octane, the knock retard is zero.
 

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How many miles did you accumulate on the BKR7Es?
I'm currently running those, but I've only had them in for about a thousand miles or so.
I have a set of BKR8EIX ready to install. I may just go ahead and swap them in.
Im curious to see if they help out on the slight amount of knock retard I'm getting on 89 octane fuel.
On 93 octane, the knock retard is zero.
The 7E actually ran better for me, but I'd have to regap ~7500 mi intervals on a stock tuned one.
 

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The 7E actually ran better for me, but I'd have to regap ~7500 mi intervals on a stock tuned one.
Ok thanks.
I havent noticed any difference on the 7Es compared to the OE replacement ACDelcos with ~30K miles on them.
But mines an automatic, if that matters.
But I am curious if the slightly colder 8s will have any effect on KR though.
 

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Mine has had hesitation in the 2500-3500 rpm range under load. After reading this, I checked the spark gap on mine. ACDelco Iridium Spark Plug 41-12. When I initially installed them. they were gapped at a loose .025. Checked them this weekend and the .030 passes loosely through. I moved them back to .025 and the car has not hesitated or stumbled since. I'm about 10k since installing them. Looks like I need to check gap on each oil change. I run stock and 87 octane 10% ethanol gas...... no on to find the coolant leak. sheeesh!
 

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The acdelco 41-121 should not be seeing any noticeable gap increase is so few miles.
My second set of 41-121s had 30K miles when I pulled them for the BKR7Es.
They were still at exactly the same gap that I installed them at...
The little platinum/iridium "pucks"
that are spot welded to the ground straps can easily come off.
Their bond to the ground strap is delicate at best.
It's not uncommon for them to fall off
While in use...
If you still have those plugs, check them to see if those pucks have come off.
That would explain your increased gap.
 
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