# Replacing my spark plugs Thursday



## kfr291 (Aug 11, 2012)

can you do a write up on a how-to?


----------



## XtremeRevolution (Jan 19, 2012)

kfr291 said:


> can you do a write up on a how-to?


There is a write-up for checking and adjusting the spark plug gaps, which is basically the same thing. 

To the OP: I believe the spark plugs are simply updated revisions of an older plug. You may find that one or the other may be discontinued or low in stock. I don't think either will cause any issues.


----------



## bodeis (Jan 28, 2012)

THe 41-121 is only for motors produced at the flint plant according to the gm parts catalog.


----------



## sciphi (Aug 26, 2011)

I'd use whichever one is in stock. Not sure what the difference, if any, would be.


----------



## obermd (Mar 3, 2012)

GM finallly settled on 0.025-0.0275.


----------



## CruzeEcoBlueTopaz (Jan 5, 2012)

Thanks for the info gentlemen.


----------



## AutumnCruzeRS (Sep 10, 2012)

So is the 41-117 plug correct in the manual. I want to get new plugs before I go pulling out the originals just incase theres any issues.


----------



## chevycruze2012 (Nov 13, 2012)

heres a quick problem solver for us cruze owners and want to change plugs or anything. Buy a KN air filter, it may cost 50 or sixty bucks but it WILL SAVE you in gas. Trust me on that. NGK which is the plugs that gm originally put in the cruzes in production are the best plugs on the market. Id go with the Iridiums from ngk. Sure they are a little pricey, actually the same cost as the delco's but the iridiums were highly designed for increased mpg, lower emissions, and better fuel burn, which means they burn less fuel to help you go farther. if anyone has a question about a part, im ur man to ask. Im a mechanic who knows his stuff lol. I say that in confidence. Thanks


----------



## AutumnCruzeRS (Sep 10, 2012)

Can you tell me if acdelco 41-117 plug is correct for the 1.4T


----------



## spacedout (Dec 7, 2010)

AutumnCruzeRS said:


> Can you tell me if acdelco 41-117 plug is correct for the 1.4T


I have also seen 41-120 & 41-121 listed for these cars. Rockauto used to list more than one of these numbers, now they only list 41-121 for 2011-2013 cruze. 

I asked on another topic yesterday if anyone knew of any difference between these plugs.


----------



## AutumnCruzeRS (Sep 10, 2012)

Do any of these part #s represent any information? I just ordered some 41-117 plugs from ebay so we will see. I think I remember someone had got ACDelco plugs and they were NGKs in a ACDelco box.


----------



## chevycruze2012 (Nov 13, 2012)

Sorry AutumnCruzeRS that it took me so long to reply back to you...According to my knowledge the 1.4L sparkplugs from AcDelco it shows in my catolog that part numbers 41-120 and 41-121 are for the 2012 models with the 1.4L. Not sure where others are getting that other number from. In fact these acdelco p/n's appear to show these plugs will go in the 1.4L and the 1.8L engines. I tried cross referencing that number in acdelcos catolog and it didnt show a cruze fitment footnote, so im assuming whoever told any of you either lied or mistaken part numbers lol.


----------



## Greasemonkey2012 (Jul 8, 2012)

i got a set of Acdelco plugs today and their gaped to .26 should i leave them or put them at .28




CruzeEcoBlueTopaz said:


> Im planning on replacing my spark plugs in my 2012 Cruze Eco with 75k miles and I need to know why ACDelco lists 2 spark plugs for my vehicle and what the difference is. Also the Cruze manual says my spark plug should be the 41-117. What did GM offically announce about the gap ? these list .28 I will upload a picture thursday of what my spark plugs look like after 75k miles and averaging 50mpg actual for anyone who is curious. Thanks for the info.
> 
> 
> 
> ...


----------



## EcoDave (Mar 7, 2013)

Be a man and gap them .035


----------



## Greasemonkey2012 (Jul 8, 2012)

Well I'm tuned tho 


Sent from AutoGuide.com App


----------



## EcoDave (Mar 7, 2013)

Whoops sorry, With a tune you should go to .028
http://www.cruzetalk.com/forum/10-e...ssion/10362-trifecta-tune-spark-plug-gap.html


----------



## Greasemonkey2012 (Jul 8, 2012)

Well why are they gapped at .26 from factories I thought gm wants them .25 to .275 


Sent from AutoGuide.com App


----------



## EcoDave (Mar 7, 2013)

From Vince @ Trifecta



> "It is true there is a discrepancy about what the gap should be - the GM
> service manuals say something like .033" or so, and the owner's manual that
> came with your car says the gap is supposed to be .028". Based on my
> experience tuning turbocharged engines, I believe the .028" to be the
> ...


From LS1LOL


> the largest spark plug gap you can run before blowout will give you the best performance possible. Think of the spark plug as a lighter, and the larger the gap the larger the flame on the lighter. You will get a more complete burn with a larger spark plug gap. I have played with spark plug gap on a few different motors (Supercharged 3800 and LS1) and I personally saw a 2 MPH gain on my Monte Carlo (S/C 3800) from opening my plug gap up from 0.035" to 0.055" (did back to back runs with that as the only difference). That specific setup was running 9PSI boost from an Eaton M90 blower


----------



## 13Cruze (Mar 12, 2013)

I thought on the other spark plug thread it was determined that the gap for the 1.4L turbo was .033" to .037"?


----------



## titan2782 (Nov 4, 2011)

13Cruze said:


> I thought on the other spark plug thread it was determined that the gap for the 1.4L turbo was .033" to .037"?


No. For tuned it's 0.028. For non tuned 0.035. 

As far as stock gaps, they should be around 0.025


----------



## 13Cruze (Mar 12, 2013)

titan2782 said:


> No. For tuned it's 0.028. For non tuned 0.035.
> 
> As far as stock gaps, they should be around 0.025


I'm a little lost, what's the difference between non tuned and stock?


----------



## XtremeRevolution (Jan 19, 2012)

13Cruze said:


> I'm a little lost, what's the difference between non tuned and stock?


I think he waa referring to the gap that you should expect to measure from the factory. Un-tuned is what we recommend you adjust them to.

Sent from AutoGuide.com App


----------



## CruzeEcoBlueTopaz (Jan 5, 2012)

I sure created an awful title for this thread.


----------



## Blue Angel (Feb 18, 2011)

chevycruze2012 said:


> heres a quick problem solver for us cruze owners and want to change plugs or anything. Buy a KN air filter, it may cost 50 or sixty bucks but it WILL SAVE you in gas. *Trust me on that.* NGK which is the plugs that gm originally put in the cruzes in production are the best plugs on the market. Id go with the Iridiums from ngk. Sure they are a little pricey, actually the same cost as the delco's but the iridiums were highly designed for increased mpg, lower emissions, and better fuel burn, which means they burn less fuel to help you go farther. if anyone has a question about a part, im ur man to ask. *Im a mechanic who knows his stuff lol. I say that in confidence.* Thanks


You should sell cars, not fix them.

K+N filters are NOT proven to increase fuel economy. Trust me on that.

If you don't trust me, trust K+N themselves. This page from K+N's website ( K&N High Performance Lifetime Aftermarket Air Filters - Automotive and Motorcycle Air Filters ) says the following:

_"Fuel economy testing and mileage claims are a tricky business. Just ask the EPA, whose website states, “EPA’s fuel economy estimates are designed to allow consumers to comparison shop. Your fuel economy will almost certainly vary from EPA’s fuel economy rating. This is based on a number of factors, such as weather, road conditions, your driving and maintenance habits, and your use of air conditioning.” A lot of exaggerated claims are made in the marketplace by products claiming to improve gas mileage. K&N makes no general fuel economy claims, however we encourage you to try our air filter for yourself. Keeping air filter restriction as low as possible can be an important tool, among others, for maintaining high mileage."_

K+N is a large well funded company with lots of high tech lab test equipment, dynos, etc. If they had any grounds to prove a fuel economy increase they most certainly would advertise it. They recommend that keeping air filter restriction low will help maintain high mileage, and changing your factory air filter regularly will accomplish just that. The main advantages of a K+N air filter are reduced restriction at high flow rates and the ability to wash and re-use the filter, neither of which has anything to do with increasing fuel economy.

You sir have just proven that you, despite what you claim, do not know your stuff. If you want to debate this, PM me instead of polluting the OP's thread. The only reason I'm posting a reply here is because you are claiming to be an expert and are posting inaccurate information that I can only hope nobody is "learning" from.


----------



## Blue Angel (Feb 18, 2011)

CruzeEcoBlueTopaz said:


> I sure created an awful title for this thread.


Now THAT's funny! 

In (late) response to your original post, check out this information from NGK's website:

NGK Spark Plugs USA

*Q: How often should I replace my spark plugs?*
_*A:* Unfortunately,there is no single answer to this question. As spark plugs grow older, they lose their sharp edges as material from the center and ground electrodes is slowly eroded away. As the gap between these two points grows, the voltage required to bridge the gap increases proportionately. Even the best ignition systems will be strained to supply enough voltage to completely burn the fuel. It is at this point, when fuel is being left unburned, that the time has come to change spark plugs.

_
_Replacing worn out spark plugs with new ones (with sharp new edges) effectively restores the ignition system's efficiency. Misfires are reduced, power is restored, economy of operation is enhanced and emissions are reduced._

This seems to be half truth and half sales pitch.

The true part is about the widening gap. This is common sense and the reason we gap plugs to begin with. If the gap on a used plug is too high it will require more voltage to properly jump the gap. This is true of new and old spark plugs.

The sales pitch seems to be the part about the "sharp edges". They claim the sharp edges are lost (eroded away) and that new plugs with new sharp edges are somehow better but don't say why...

If it were me looking at a set of well used plugs, I would do the following: Check the gap. If the gap is still within factory specs, there is no obvious buildup of foreign material on the plug, and there doesn't appear to be significant erosion damage to the tip or ground, I would just put them back in the engine and keep on motoring.

If all of the above checks out but the gap is a little wider than the spec, I would re-gap them to the proper spec, put them back in and keep on motoring. I have done this with great success in the past, but as with everything there is probably a limit to the amount of re-gapping a plug can take and still work properly. Once or twice is probably OK but I have no proven data to back that up. I have measured original iridium plugs at 160,000 km (~100k miles) and the gaps were still in spec.

If the gap is WAY out of spec, most likely you would see significant erosion damage to the tip and/or ground. In this case I would replace them.

If the engine is obviously not running right and you suspect a spark plug is at fault after diagnosis, replace the plugs.

I have not fully researched the topic of spark plug wear/replacement, so there surely are things I don't know. I'm passing on what I feel is my own correct experience. Feel free to research further and, if in any doubt, refer to the service manual. If you find new data that contradicts what I've said, please present it here so we can all study it and maybe learn something new.

Keep up the Cruzin - your average MPG are in elite territory!


----------



## 70AARCUDA (Nov 14, 2010)

addendum -- electrons are emitted from sharp edges or needle points FAR easier than from smooth, rounded surfaces. So, the OP's comments about gaining back some of the ignition perfomance that was lost due to the dulled gap "edges" is 100% valid when/if we're talking about OLD style spark plugs...however, with todays use of single- and double-iridium/platinum 'button' plugs, there's not much you can do to restore sharp edges once they've eroded, because these exotic metals are VERY hard/brittle they do NOT take well to being filed.


----------

