Round Delphi or square Mitsubishi ignition coils

  • 5.3L
  • V8
  • 4WD
  • 190,000 MILES
I have a 1500 suburban. I’ve done a ton of research and can not find out whether mine takes round or square ignition coils. All forums point to both and preference. Is that correct? Can I use either one or does it have to match? From what I read back when these were made they used whatever was on the shelf. I have a set of round now but need to know if I can use or have to get the square. My 8th digit in vin is Z

Please help?
Do you
have the same problem?
Thursday, April 11th, 2019 AT 8:48 AM

1 Reply

Hi Anthony,

Thanks for the question. For those that say this doesn't matter unfortunately they are incorrect. There is a difference and it is flex fuel vehicles vs non. Most people will not have an issue if they never run E85 in their flex fuel vehicles. However, if you have a "Z" VIN then you need these coils in the event you run E85.

Also, the best way to find out which one you need to use is to look at the one that is currently in the vehicle. Reason being, many people have changed the engine in these vehicles and did not think about making sure they are replacing the engine with the same engine that was in it. Both will work so you could have a Z VIN and not have a flex fuel engine anymore.

I have included the stamping number for each so you can find out what is in your vehicle and whether it is correct for your VIN. However, Z VINs require the square coils.

The other main issue I have when people say, "both work, don't worry about it, " is because if both work then there would not be a difference. Automotive suppliers do not make duplicate parts in two styles with two different part numbers just because they feel like it. This is bad business and they don't do it. There is a reason and even if both work on regular fuel, the engine was tuned and PCM calibrated to work with what the engineers designed it for. Altering that may not cause an immediate issue but I am always in the camp of, the engineers knew what they were doing in situations like this. Improvements on parts/design can be made but this is not one of those cases. They intended for one coil to go in one style engine and the other to go in the other, so if it were my vehicle I would go with what they suggested.

Again, you could put the round in it and see if you have issues but if you want to stick with what GM called for, you need the square.

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Friday, April 12th, 2019 AT 12:59 PM

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