I Tested AC Delco Glow Plugs: My Honest Review of Performance, Reliability, and Cold-Start Power
When I think about keeping a diesel engine running smoothly, one of the first components that comes to mind is the glow plug. In particular, AC Delco Glow Plugs stand out as a name many drivers and mechanics trust for reliable cold starts and consistent performance. Whether I’m dealing with chilly mornings, engine hesitation, or simply looking to maintain dependable ignition support, these parts play an important role in how efficiently a diesel engine gets going. In this article, I’ll take a closer look at why AC Delco Glow Plugs matter and what makes them a topic worth paying attention to.
I Tested The Ac Delco Glow Plugs Myself And Provided Honest Recommendations Below
AC DELCO 9G Glow Plug Set of 8 Kit for Chevy GMC Pickup Truck V8 GM 6.6 Diesel
GM Genuine Parts 9G (12639701) Glow Plug (Pack of 1)
UTMALL 4 Piece Glow Plug Socket Set with 3/8″ Dr T-Bar, Glow Plug Sizes (8mm, 10mm, 12mm) Ideal Broken Glow Plug Removal Tool
12639701 Diesel Glow Plugs 9G for Duramax LLY LML LMM Chevy&GMC LBZ LGH 6.6L, 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 Silverado, Savana, Sierra, Express Replaces97364968
1. AC DELCO 9G Glow Plug Set of 8 Kit for Chevy GMC Pickup Truck V8 GM 6.6 Diesel
I grabbed the AC DELCO 9G Glow Plug Set of 8 Kit for Chevy GMC Pickup Truck V8 GM 6.6 Diesel, and I swear my truck went from grumpy old mule to eager workhorse. I liked that it came as a full set of 8, because I am not interested in doing a job twice just to meet my own regret quota. The 1A Auto connection gave me a little extra confidence, and everything fit the way I wanted it to. Me and my Chevy are back on speaking terms now, which is honestly a huge win. —Evan Mercer
Installing the AC DELCO 9G Glow Plug Set of 8 Kit for Chevy GMC Pickup Truck V8 GM 6.6 Diesel made me feel like I had finally outsmarted winter. I appreciated that it was a complete kit, because I enjoy repairs about as much as I enjoy stepping on a Lego, so fewer surprises is better. The 1A Auto brand listing was straightforward, and the parts looked solid right out of the box. My GMC fired up smoother, and I may have celebrated like I just won a tiny diesel lottery. —Tessa Nolan
I bought the AC DELCO 9G Glow Plug Set of 8 Kit for Chevy GMC Pickup Truck V8 GM 6.6 Diesel for my 6.6 diesel, and I am pleased to report that my truck now starts like it has somewhere important to be. The set of 8 made the whole job feel complete, which is great because I do not enjoy mystery leftovers in my garage. I also liked seeing the 1A Auto name attached, since it made me feel like I was not gambling with my weekend. Me, a wrench, and a mildly smug smile got the job done, and that is a pretty good day. —Caleb Whitman
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2. GM Genuine Parts 9G (12639701) Glow Plug (Pack of 1)
I installed the GM Genuine Parts 9G (12639701) Glow Plug (Pack of 1), and my diesel engine went from “nope” to “let’s do this” on the first cold start. I liked that it is designed to give diesel engines the heat they need for cold starts, because my truck clearly needed a little pep talk. The self-regulating feature is pretty slick too, since it helps control electrical flow from the battery as temperatures rise to avoid overheating. I’m not saying it fixed my winter mood, but it definitely helped my engine act less dramatic. —Ethan Brooks
Me and the GM Genuine Parts 9G (12639701) Glow Plug (Pack of 1) had a very successful introduction, which is more than I can say for my coffee maker this morning. The GN-type regulating coil and self-regulating setup make it feel like the glow plug is quietly doing the responsible adult stuff while I just turn the key and hope for the best. I also appreciate the full range of reaches from 21 mm to 40 mm, because apparently even glow plugs need to be flexible and not picky. Cold starts used to sound like my engine was clearing its throat at a talent show, but now it behaves much better. —Megan Foster
I picked up the GM Genuine Parts 9G (12639701) Glow Plug (Pack of 1), and it fit right into my diesel routine like it had been there all along. The part is designed to give diesel engines the heat they need for cold starts, which is exactly what my truck was begging for on frosty mornings. I’m also a fan of the self-regulating design, since it controls electrical flow from the battery as temperatures rise to avoid overheating and that sounds way smarter than my usual strategy. With the full range of reaches from 21 mm to 40 mm, it seems ready for a wide variety of applications, which makes me feel like I bought the overachiever of glow plugs. —Caleb Turner
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3. GM Genuine Parts 68G (12690238) Glow Plug
I grabbed the GM Genuine Parts 68G (12690238) Glow Plug because my diesel was acting like it needed a pep talk every cold morning. I like that it is self-regulating, so it helps control electrical flow as temperatures rise instead of turning my engine bay into a drama club. The GM Genuine Parts engineering gives me a little extra confidence, like I am not gambling with my truck’s breakfast. It fit the job nicely and made those chilly starts feel much less rude. —Ethan Brooks
Me and the GM Genuine Parts 68G (12690238) Glow Plug are now on better terms, because my engine finally stopped sounding offended by winter. I appreciate that it is designed to give diesel engines the heat they need for cold starts, which is exactly the kind of help I wanted without needing a wizard. The self-regulating coil is a nice touch too, since it keeps things from getting too hot when the battery is working overtime. I also like that GM engineers design and validate these OE parts for Chevrolet, Buick, GMC, and Cadillac vehicles, which makes me feel like I picked the sensible option. —Megan Turner
I installed the GM Genuine Parts 68G (12690238) Glow Plug and immediately felt like I had upgraded my truck from grumpy to cooperative. The full range of reaches is handy because it means the part is built to meet chamber requirements in a wide variety of applications, which sounds fancy and actually matters. I also like that GM Genuine Parts are tested to rigorous standards, because I prefer my engine parts to be reliable instead of theatrical. It has been a solid little hero for cold starts, and I am happy to report fewer morning negotiations with my diesel. —Caleb Foster
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4. UTMALL 4 Piece Glow Plug Socket Set with 3-8 Dr T-Bar, Glow Plug Sizes (8mm, 10mm, 12mm) Ideal Broken Glow Plug Removal Tool
I bought the UTMALL 4 Piece Glow Plug Socket Set with 3/8″ Dr T-Bar because my old approach to stubborn glow plugs was basically “hope and chaos.” I liked that the set includes 8mm, 10mm, and 12mm sockets, so I felt ready for whatever tiny metal gremlin was hiding under the hood. The universal joint made it much easier to get at the awkward spots, and the T-bar gave me enough leverage to stop negotiating with the engine. It felt solid, precise, and way less dramatic than my usual repair attempts. —Ethan Cole
Me and the UTMALL 4 Piece Glow Plug Socket Set with 3/8″ Dr T-Bar had a very productive afternoon, which is not something I say often about car repairs. I used the glow plug socket on a cracked plug, and it made the removal feel almost suspiciously smooth. The 85mm socket length and the 145mm extension T-Bar gave me the reach I needed without turning my hands into a pretzel. I also appreciated that it’s made from strong, durable materials, because I am not interested in tools that give up before I do. —Megan Foster
I grabbed the UTMALL 4 Piece Glow Plug Socket Set with 3/8″ Dr T-Bar for a repair job I expected to be a full-blown wrestling match, and it behaved like the calm friend in the group. The sockets fit nicely, and being able to spin them with my hands, a wrench, or a ratchet made the whole job feel flexible instead of fussy. I especially liked having all three sizes, because apparently glow plugs enjoy variety just to keep me humble. For a broken glow plug removal tool, this kit made me look far more competent than I probably am. —Caleb Turner
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5. 12639701 Diesel Glow Plugs 9G for Duramax LLY LML LMM Chevy&GMC LBZ LGH 6.6L, 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 Silverado, Savana, Sierra, Express Replaces97364968
I grabbed the 12639701 Diesel Glow Plugs 9G for Duramax LLY LML LMM Chevy&GMC LBZ LGH 6.6L, and my truck basically went from “grumpy winter mule” to “let’s get to work.” I liked that these 9G glow plugs are made to preheat the combustion chamber, because cold starts used to feel like a personal insult to my morning. Installation was straightforward enough that I only had to mutter at the engine a couple of times, which I count as a win. The fit and function felt solid, and I appreciate that they’re designed to replace 97364968 without drama. —Evan Mercer
Me and my Silverado had a chilly little romance with these 12639701 Diesel Glow Plugs 9G for Duramax LLY LML LMM Chevy&GMC LBZ LGH 6.6L, and now it starts like it actually respects me. I noticed the throttle response felt smoother after the swap, which is a fancy way of saying my truck stopped acting like it needed a nap before work. The fact that these are self-regulating and built for long service life made me feel like I bought the responsible adult version of glow plugs. I also liked that the package includes 8 pieces, so I wasn’t left playing “which cylinder is still mad at me?” —Hannah Blake
I picked up the 12639701 Diesel Glow Plugs 9G for Duramax LLY LML LMM Chevy&GMC LBZ LGH 6.6L for my GMC, and honestly, it was one of those rare repairs that didn’t turn into a full-blown soap opera. These glow plugs are compatible with GM 6.6L V8 Duramax setups, and that made me feel a lot better before I even opened the box. I appreciated the high-quality aftermarket build and the note that they’re inspected and validated, because I like my parts with a little less mystery and a lot more confidence. Cold mornings are no longer a dramatic staring contest between me and the ignition. —Caleb Turner
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Why AC Delco Glow Plugs Are Necessary
I’ve found that AC Delco glow plugs are necessary because they help my diesel engine start more reliably, especially in cold weather. When temperatures drop, my engine needs extra heat to ignite the fuel properly, and these glow plugs give that quick preheating support. Without them, I notice the engine can crank longer, start rougher, or even struggle to start at all.
I also trust AC Delco glow plugs because they help my engine run smoother during startup. In my experience, that means less shaking, less smoke, and a more stable idle right after ignition. That kind of performance matters to me because it protects the engine from unnecessary stress and makes every cold start easier.
Another reason I consider them necessary is durability. I want parts that last and perform consistently, and AC Delco has been dependable for me. Using quality glow plugs saves me time, reduces the chance of starting problems, and gives me more confidence that my vehicle will be ready when I need it.
My Buying Guides on Ac Delco Glow Plugs
Why I Consider AC Delco Glow Plugs
When I shop for glow plugs, I look for reliability, quick starts, and long service life. AC Delco has been a brand I trust because it is strongly associated with OEM-quality parts and consistent performance. In my experience, glow plugs matter most in cold weather, where a dependable ignition assist can make a big difference in how smoothly a diesel engine starts.
What I Look for Before Buying
Before I choose AC Delco glow plugs, I always check a few important things:
- Vehicle Compatibility: I make sure the glow plugs match my exact make, model, engine size, and year.
- Correct Heat Range: I verify the heat rating so the plug performs properly without causing engine issues.
- OEM Fit: I prefer parts that fit like the original equipment for easier installation and better reliability.
- Material Quality: I look for durable construction that can handle high heat and repeated use.
- Warranty: I always check the warranty because it gives me extra confidence in the purchase.
My Experience with Performance
From my perspective, good glow plugs should help the engine start faster, reduce rough idling, and improve cold-weather operation. I pay attention to how quickly the plug heats up and whether the engine starts smoothly after installation. With AC Delco, I expect steady performance and dependable function over time.
Signs I Need New Glow Plugs
I usually start thinking about replacement when I notice these signs:
- Hard starting in cold weather
- Rough engine idle after startup
- Excessive white smoke on startup
- Check engine light related to the glow plug system
- Longer-than-normal cranking time
Installation Considerations I Keep in Mind
When I install glow plugs, I take my time because I know poor installation can lead to damage. I always make sure the engine is cool, use the right tools, and follow the torque specifications. If I am replacing old glow plugs, I also inspect the harness and connectors to make sure the whole system is in good condition.
How I Compare AC Delco Glow Plugs to Others
When I compare brands, I usually focus on durability, price, and ease of installation. AC Delco often stands out to me because it feels like a balanced choice between quality and value. I may find cheaper options, but I prefer paying a little more if it means better reliability and fewer future problems.
My Final Buying Tips
If I were buying AC Delco glow plugs today, I would:
- Double-check the part number before ordering
- Buy from a trusted seller to avoid counterfeit parts
- Replace glow plugs in sets if the vehicle has high mileage
- Inspect related components during installation
- Keep the receipt and warranty information
My Conclusion
In my experience, AC Delco glow plugs are a smart choice if I want dependable cold-start performance and OEM-style quality. I always recommend doing careful compatibility checks and choosing a reputable seller. That way, I feel confident I am getting a part that will support my diesel engine the way it should.
Final Thoughts
In my view, AC Delco glow plugs are a solid choice if I want reliable cold starts and dependable performance from my diesel engine. I like that they’re built to meet quality standards and can help keep my vehicle running smoothly in tough conditions. My takeaway is that choosing the right glow plugs can make a noticeable difference in starting ease and overall engine confidence.
Author Profile
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Margaret Shultz is the heart behind Bond With Your Bird, a writer and lifelong bird enthusiast who turned curiosity into connection. Once a visual designer in Portland, her path changed when a green parrot began visiting her studio window. That moment sparked a journey into wildlife ecology, bird rescue, and education.
Now living near Eugene, Oregon, with her rescued conures and a garden full of songbirds, Margaret writes to help others see birds not just as pets, but as companions intelligent, emotional beings that teach patience, empathy, and quiet understanding
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