Alright guys, so here is my question.
I'm looking at a couple different AC Delco spark plugs, I went to their website and searched all the plugs compatible with my '99 GMC Jimmy. There were a bunch of plugs that all looked the same (except different color metals) and were all listed as "Professional Iridium Plugs". Here are the part numbers:

41-943
41-948
41-950
41-963
41-993

What exactly is the difference between these, if any? Are they just upgraded versions as the numbers rise? I'm looking to buy 6 of one of these part numbers just to give my ride a tune up. Suggestions?

 

Probably different heat ranges.

I think the 4.3l engines 2nd gen. calls for platinum or double platinum. I think the iridium is a more controlled spark...I could be wrong, if I am, I stand corrected.

 

Differences are the material that the center and ground electrodes are made of. Single Platinum, Double Platinum, Single Iridium, Double Iridium, etc. Originally your '99 Jimmy came with 41-932, the new number is 41-993, (Double Iridium). Platinum doesn't last as long as Iridium.

 

so would you recommend I put in 41-993 for best performance/life span?

 

That's top shelf stuff, yes.

 

so when I go on ebay, i click on the compatibility with my '99 Jimmy SLT and it says its not compatible...(41-993) is this just an error and will it really fit? looks like it would, I just want to make sure.

 

Gotta be an error. AC Delco 41-932 (double platinum) was original equipment but it was upgraded to AC Delco 41-993 double iridium.

 

thank you I'll order them now, just wanted to make sure!

 

Be careful where you buy the 41-993. Amazon and eBay are full of super low priced 41-993 iridium spark plugs that are junk imported clones. I'd highly recommend that everyone stay away from those 2 sight when buying auto parts. You never know what you will receive. Stick to Rockauto or another reputable seller. If you look on You Tube there s a bunch of videos on how to determine if the iridium plugs you received are clones. Real ones for example come with a cardboard tip protector while the clones use plastic. Quality of the laser etching is also way better on the real ones. Some clones even have spelling errors on the plugs and boxes. The clones have been know to fail almost immediately. Some had the tip melt off. Wouldn't want that in your cylinders.
BTW 91-432 is no longer manufactured and near impossible to find or ridiculously priced when you do find them.

 

I just use the good old copper spark plugs. R44LTS6 Now on my second set in 70K miles. Only advantage of irridium or platinum is length of service. The copper plugs are actually documented to work better as a spark plug.

Here's just one of many articles that can be found on the subject. https://www.autozone.com/diy/spark-p...the-difference