Iridium Spark Plugs kill Fuel Economy?

[TABuickMike]

Ok so our T-Type had AC plugs in it and I felt like they could use a changing and when taking them out 3 of em broke, which further added to my feeling. Before I replaced the air filter (was full of black goo it was so old) and the AC spark plugs (a little worn) the car would get 19mpg city and 21mpg highway. After putting in a new air filter and some NGK Iridium IX UR4IX plugs I cant get better than 17ishmpg on the highway and even worse city. I havent raced the car since but it feels like it still pulls the same and it still behaves the same as far as knock.

My question is, what about these plugs could be killing the gas mileage? (I realize they're a little hot but I rarely jump on it, and that they're Iridiums but I thought that was better). I had to get the car back up and running and didnt have time to regap them from .035 to .032. The car is all stock to my knowledge except for a chip.

 

[turbo nasty]

HMMM is it the same heat range? You said they are a lil hotter.

NGK heat range is different from most plugs. They scale them.... low number is hotter and higher is colder.

 

[TABuickMike]

Hotter is a lower number for them according to the chart so 4 is hotter than 5, 5 hotter than 6 etc.

 

[turbo nasty]

low number is hotter and higher is colder

Yep thats what I was saying.

So you are colder by one heat range on the new iridium?

If the car has been sitting for a while it may just need a few fresh tanks of gas to get the MPG back up.

 

[turbo nasty]

Double post oops

 

[TABuickMike]

Yep thats what I was saying.

So you are colder by one heat range on the new iridium?

If the car has been sitting for a while it may just need a few fresh tanks of gas to get the MPG back up.

Well everyone seems to prefer NGK UR5s which means my NGK UR4IKs is one hotter than what most run/recommend. The car gets driven at least every weekend and when I was getting the mpg I stated above it was driven everyday. The mpg drop was instant so I dont think it was anything but the plugs? I just dont see why one range hotter plug and the fact its Iridiums would kill mpg so much, especially because I thought the Iridiums were much better. Could the gap being a little big do something? This is under partial throttle cruising not under boost, I dont see why it would.

 

[Nasty Wendy]

I guess AC plugs just don't cost enough huh?

 

[TABuickMike]

Im on a mini mission to see what kinda fuel economy I can get out of the car so one of my plans was getting new spark plugs and I figured these would net me a little better economy, buuuut that wasnt the case so I was hoping I could get some help as to why.

I guess AC plugs just don't cost enough huh?

 

[Nasty Wendy]

Im on a mini mission to see what kinda fuel economy I can get out of the car so one of my plans was getting new spark plugs and I figured these would net me a little better economy, buuuut that wasnt the case so I was hoping I could get some help as to why.

Every so often the topic of spark plugs comes up for Turbo Buicks. As the 'Old Guys' thin out the point that AC Delco or Autolite plugs perform as good as anything you can put in that hole starts to not be made. As the younger generation owners grow in number we lose touch with some of the knowledge and established facts of the elders. Trust me EVERY spark plug known to man has been tried in these 3.8 Turbo V6s and while some will like something else the truth is that no other plug offers any measurable gain over a set of ACs or Autolites. Save your money. When I change the plugs in my motorcyle I WISH I could use cheap plugs or even in my Lightning for that matter.

 

[turbo nasty]

Im on a mini mission to see what kinda fuel economy I can get out of the car so one of my plans was getting new spark plugs and I figured these would net me a little better economy, buuuut that wasnt the case so I was hoping I could get some help as to why.

Easy way to tell is get some regular NGK's one heat range colder and try em. Not expensive and then youll have another set of plugs as back up.

FWIW I have tried Bosch +4's, splitfires, AC rapidfires and I saw no difference honestly.
Autolite, AC and NGK's are my fav. NGK's seem to have teh best ground strap and electrode centering outta the bunch.

 

[TABuickMike]

I thought I'd try to be on the edge of technology, made sense that technologically newer plugs would be better than regular ones despite what my dad says, guess I had to be proven wrong to believe so. Either way if thers no advantage over regular plugs why are these such a step backwards

 

[Dino1]

Plugs

Iridium plugs.... boost of any sorts or Nitrous don't go well together. The electrode is very small and the spark either get blown out or the electrode melts away. This is common knowledged in the world of high performance.

Fancy spark plugs are nothing more than snake oil, the proper plug,, heat range, and reach are the key to the proper plug. Keep them changed and the edges sharp on the electode and strap and you will be good. You can cut back the strap, but not needed unless you are running mega boost or high compression around 15:1+ with meth or nitro.

 

[turbo nasty]

Good point Dino.......

Once your 90 degree/sharp edges has worn off the center electrode, your ign loses 30-40%.

Its real important

 

[davidf]

I guess AC plugs just don't cost enough huh?

I paid 1.99 for each of my UR5's at Autozone.

 

[turbo39151]

I stick with AC Delco. BTW, have you considered running some seafoam through the car? If the air filter was that gunked up I can just imagine what the rest of the insides look like. I don't think it can hurt...

 

[DR BOOST]

on a gm dis ignition, dont three plugs fire backwards? that would explain why specialty plugs dont work well.

 

[machinegun]

OK so standard AC delco plugs worked well even worn.

Fancy plugs dont work.

Answer is dont use fancy plugs.

That maybe a little too harsh.

I have played with more spark plugs than I care to mention. I have probably tried every new plug just for grins. I have tried them at low boost high boost pump gas race gas pump gas alky race gas alky 100 octane 105 110 116 123. For my preference and my customers cars, the good old CR43TS CR42TS from AC Delco seem to work the best. They give me the best performance, best fuel economy and of course this means the best bang for the buck. From my personal experience I have had great luck with wat seems to work.

Now I need to get some of those fancy E3 diamond fires and try them out.

 

[V6UnderPressure]

Iridium plugs.... boost of any sorts or Nitrous don't go well together. The electrode is very small and the spark either get blown out or the electrode melts away. This is common knowledged in the world of high performance.

FTR, that is completely not true. If boost of any sorts never went well with iridium plugs, then they wouldn't work on EVO's pushing 30psi. And thats their FACTORY plugs. Do you know how many people running boosted cars are running iridium plugs!!!??? It may not work in the buick world, but it sure as hell works everywhere else. Different things can come into play such as placement of the plug in the head etc. etc. etc. Need to check that common knowledge.

DR BOOST is also mistaken. The plugs are not firing backwards. Because I am faster than DR BOOST, it just seems like hes going backwards. All kidding aside, I surprisingly believe DR BOOST is right? Three fire from the center electrode to the outer, and the other three from the outter to the center, correct? The outter to the center firing would have a tough time with such a small electrode. Maybe someone can chime in here and clarify, but I believe this has something to do with the whole "waste spark" thing? I believe RJC was working on a set of two coil packs working in conjunction with each other in order to eliminate waste spark, and I believe this would have cured the problem, and allowed us to use the Iridium plugs. At any rate, you would think with this issue that AC delco would have made a plug for our cars with the same size center and outer electrode.

"Smallest tip diameter available Iridium / Platinum surfaces ensure slow wear rate providing stable idle, superior anti fouling, improved fuel efficiency and lower emissions"<-----With this sales pitch, I don't blame TABuickMike for giving them a try.

 

[Roger]

Dutweller went from a regular plug to iridium in a blown Fxxx & picked up over 200 hp, years ago.
I'm interested in iridium & this is the first Buick thread I've seen with iridium plugs. I do have a set in my toolbox, however, the ur5 plugs in the TR now have been doing fine.

 

[rattrod30]

That air filter "full of black gunk"

Was probably a K&N . What did you replace it with ?