View Full Version : Which spark plugs to buy?

07-28-09, 02:10 PM
93 Northstar Allante
My service manuals calls for .045 gap spark plugs. I went to Rockauto and the following is listed for my car. Which is the best spark plug?

ACDelco 41-936 Platinum Plug (.060 gap) – $5.99
NGK 7164 IX-Series Iridium (.060 gap) - $6.90
DENSO 5325 IT16 Iridium power (World’s smallest center electrode) - $8.01
NGK 7740 Premium Platinum - $8.14
NGK 3403 GP Series Platinum - $2.60

Why are all the plugs recommended for my car set at .060 gap when the manual calls for .045? Should I use ACDelco 41-987 plugs used on newer Northstars which are gapped .050?

07-28-09, 03:35 PM
do a search for "spark plug" on here...I'm sure the answer will be Delco

07-28-09, 04:11 PM
Either go to a Cadillac parts desk and ask for the latest Service Bulletin info on your car or subscribe it to www.alldatadiy.com. Look up the tuneup specs. OR, the ol' standby: pop a beer and Google.

Use the ACDelco Professional platinum plugs. IF you get a high rpm or heavy load miss close the gaps to .050", but be sure to use the proper gapping tool and DO NOT bend the center electrode or damage the platinum discs on the ground electrode.

07-28-09, 04:24 PM
I was leaning on the DENSO 5325 IT16 Iridium power (World’s smallest center electrode) for longevity and the fact that newer GM cars are using it. If it's a waste of money, I'll go with ACDelco 41-936 or 41-987.

07-28-09, 04:33 PM
For some reason - black magic - Northstars do not take kindly to plugs and electrodes other than the (original equipment) DENSO Platinum and the later Japanese-made ACDelco Professional Platinums. (Any guesses as to what company makes ACDelco Japanese plugs ???)

There are some real nasty stories in here concerning the Bosch 2 - 3 - and 4 electrode plugs. A few more about NGK.

Nobody complains about the ACD's, so why push your luck ?? Longevity ??? Isn't 100,000 miles enough as recommended for the original plugs ???

BUT, I use only NGK Iridium plugs in my Olds 455 marine engines. Not a problem. Northstars hate 'em. Go figure.

07-28-09, 05:16 PM
I'd go with the Delco as well.

07-28-09, 05:22 PM
I'll probably go with the ACDelco's but did come across a member on this board who had success with Denso Iridium's. That said, I do plan to drive the car at least another 300k miles.
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Re: Rough running 95 SLS
I can say that the Delco wires hold up much longer than other brands. I had a set of Bosch wires in my car that started missing after about 40k. The AC's regularly go to 90k+.

I'm currently running Denso Iridium plugs. Those seem to be good.

I think in the end its a longevity thing, with the Delco products being designed to GM's spec of lasting 100k miles. In reality, I think this equates to them being of higher quality.

07-28-09, 07:13 PM
With modern plug technology, unleaded fuels and today's fuel additives just about any spark plug will go 75,000+. It ain't like the 60's when a set of plugs was complete toast at 5,000 to 8,000 miles.

07-31-09, 10:31 AM
Has anyone had any experience with Pulstar Plugs at all? I understand that most recommend AC Delco due to familiarity but I'm asking if anyone has had experience with Pulstar spark plugs or knows anyone who has. I just bought a 2004 DTS and plan on getting it tuned up within the next couple weeks and plan on replacing them. I might even try to do it myself, I hear its pretty easy with the N*

Thanks in advance for any input

07-31-09, 12:37 PM
There's another post of yours similar to this in another thread, and there's an answer about the Pulstar plugs.

No one in here uses the ACDelco plugs due to or because of familiarity. This set of forums is full of spark plug stories over the last 6 years and the bottom line is that the ACDelco professional Platinum plugs in the recommended heat range are the best plugs for your engine. We've all tried various magic plugs and snake oils and the general consensus is that they either don't work, cause nagging misses and poor engine operation, or give you nothing in the way of improvement or bang for the buck. The Ac's will go to 100,000 or more.

The overall plug change is not as easy as it looks.................Do it with the engine COLD and check the boots for tracking and the coil cassettes for proper ground spring clean contact. Don't worry about a tad of oil in a plug well or two - the wells are sealed with O-rings and may tent to weep a bit. Normal.

08-04-09, 12:32 PM
Due to cost and personal experiences, I use Bosch platinum plus in my Northstar rebuilds. I give my customers the option of paying 7+ a plug or 3+ a plug and most use Bosch. I would estimate 25 or so have chosen Bosch and NONE have experienced any issues. Submariner is right on, just about any plug will last a very long time.

08-04-09, 10:30 PM
Due to cost and personal experiences, I use Bosch platinum plus in my Northstar rebuilds. I give my customers the option of paying 7+ a plug or 3+ a plug and most use Bosch. I would estimate 25 or so have chosen Bosch and NONE have experienced any issues. Submariner is right on, just about any plug will last a very long time.

WOW! First time I've heard that.

08-05-09, 09:20 AM
Having experience with Robert Bosch plugs in other vehicles and a couple of boat engine installs, I would not use a Bosch plug in even my Briggs&Stratton lawnmower. Porsches love 'em, however.

Even though the recommended ACDelco plugs for my engine are about $4 apiece more expensive than the platinum Bosch, that insignificant cost is immaterial in the scheme of an engine rebuild.

Which begs the tongue-in-cheek question: :devil: If you're buying the Bosch plugs for $1.86 each, what are you selling them to the customer for ??

08-05-09, 05:14 PM
saving $25 on a $3k or more engine rebuild is money well spent? thats like throwing a deck chair off the titanic.

08-06-09, 02:43 AM
I didnt listen I went with NGK some thing the ones with the fine tip plats. Ever since then it just seams off... a worse suge at idle then what I started with and I swear I could be wrong but weaker acceleration..

08-09-09, 01:22 AM
Hi I'm new to this forum and Cadillacs. Two weeks in fact .I tuned it up the first day. When I pulled the plugs it was at 114000.They were NGK's. Now with that much mileage you could assume they were in there 30 to 50 thousands miles.When I checked them the center electrode was eaten up 2/3's.Now to me that doesn't say much for NGK. needless to say I went with AC Delco . I couldn't care less about the price of the plugs.Just my two cents