The Most Fuel Efficient Spark Plugs

[froggy81500]

Originally Posted by dkjones96

Not every company is perfect. I've found NGK Iridium IX plugs(top of the line for them) that are +- .010" from the gap it should be set to(specified on the box), that's enough to cause problems in ESA equipped cars, reduced fuel economy and cause a rough feeling idle. I can explain why if anyone needs to know.

That gap out of the box issue is the reason why plugs should never be installed without checking the gap first. There is no telling if they were ever correct for what they are going into. And there is no telling how many times the clerk at the part store dropped them before reaching your hands. Always check the gap before installing. You'll thank yourself later.

[fowljesse]

As far as I know, Silver tip plugs have the least resistance, and have gained 3 mpg for my car, but lower resistance generally equals less life, and they're much more expensive. They're mostly used for racers that want to squeeze out every last HP. For less pollution, they are the best IMO. For cost effectiveness.... not so much. Beru is one brand. I can't remember the other.

[GasSavers_RoadWarrior]

Hmmm 10,000 ohms per foot in the spark wires, 5,000+ in the in plug resistor, and the change from copper to silver at the tip for 0.05 Ohms difference there is gonna make how much difference? Nickel or platinum stop the surface oxidising and may catalyse some of the reactions that go on in the chamber. Iridium is known to have a low work function and may enhance spark formation when warm in vacuum, due to the easier ejection of electrons from it.

[RightontheMarc]

I have been wondering about this question myself. I am looking for decent copper plugs as I like to regap my plugs often. I notice even after 20,000 miles or so even platinums foul with that white colored corrosion. Regapping my plugs always gives me slightly better gas mileage. This winter my mpgs were in the dumps at 26mpg for two fillups. After regapping then coming to this site and covering my grill and radiator it went up to 31 which still stinks but was a little better. The problem is platinums can be dangerous if not regapped carefully.

[VetteOwner]

Originally Posted by froggy81500

That gap out of the box issue is the reason why plugs should never be installed without checking the gap first. There is no telling if they were ever correct for what they are going into. And there is no telling how many times the clerk at the part store dropped them before reaching your hands. Always check the gap before installing. You'll thank yourself later.

lol im betting you those plugs fit about 20 other cars and trucks... all with different gaps. they are NOT anywhere near gapped to what their supposed to be. you MUST re-gap them (its usually on the emissions sticker under the hood somewhere) and put the silver anti seize on the threads. then put dielectric grease in the boots (if they say "already have dielectric" usually its never enough) if you drop em or slam em hard when dropping them in the holes you better recheck the gap...

[dkjones96]

They do fit other cars with different gaps 90% of the time. For example, my car takes a .039 gap but plugs come for it at .040 that's no big deal at all. If you take into account wear over the life of a copper plug compared with an Iridium plug you could actually put a long life plug like the Iridium into an engine that takes a .039 gap and have the Iridium at .044 no problem over the life of the plug. The field effect of the fine wire tip lets you gap out further at the same firing voltage than its copper counterpart.

Our Pulstar plugs work great and people see gains in cars gapped at .040, even if the car stock took a .060 gap(Dodge). Now, you will notice less performance if you were to gap your stock plug down to .040 from .060.

The problem lies when the gaps aren't consistent. A .040 gap on 5 plugs and one at .035 will mean that one cylinder fires earlier(smaller gap means less voltage meaning the ignition coil will achieve firing voltage earlier) so the knock sensor goes off and the ECU retards timing, however, the other 5 cylinders weren't knocking and this will lower the efficiency of them resulting in lower fuel economy and less power.

[usxpop]

I have a '95 Miata. Switched to platinum Bosch. Dropped about 3-4 mpg. Went back to specified NKGs and milage returned. NKG were the standard, non-exotic metal plugs found in eveything from lawnmowers to big, fire breathing V8s.

[fowljesse]

As for wires, I shorten mine. I don't know if it makes a significant difference, but I took 6 feet off my current ones (V6). I just pull off the distributer end metal with needle nose pliers, cut the wire to length, and crimp the piece back on.