Can spark plug type really effect MPG?

[FZ1]

Some vehicles are picky about plugs. Toyota only like Denso or NGK. Other vehicles will fire and run well with pretty much anything you can stuff in the hole. I always use whatever they came with originally .

Paco

This^^^^^^^

 

[TumblrDucks]

Denso claim their U-groove plug can make about 1-1.5% improvement on power and measurable improvement on MPG. I personally didn't feel any difference.

 

[burbguy82]

4.0 Jeep, loves copper champions

As I understand it, the difference in materials is for durability, not conductivity.

Copper is no problem, but will they last as long as Iridium? No.

 

[Bud_One]

All mine get Copper or platinum. My Dodge Ram says to use 2 copper plugs/ cylinder. They always look new when I replace them at the 30k interval. My guess is they want them changed at that time so they don't weld themselves in the head.

I have a co worker with a 2012 Ram with the Hemi and has the original plugs in it with over 150k on it... he won't change em.. and hasn't had any ignition issues . He bought it new.

 

[bobdoo]

And require more power to do so. Parasitic power from the alternator, which will be harder to turn, which may decrease performance. It is important to include this.

That isn't how it works.

The same amount of power (to charge the coil) will be used regardless of the resistance at the spark plug gap.

 

[KevinMalone]

A spark plug that produces a more energetic spark, like one with a larger gap, will cause a faster flame growth. This has a similar effect to advancing the ignition timing, since most of the combustion will occur sooner.

The result of this is more power and better efficiency at moderate to high engine loads where more advanced ignition timing is beneficial. The likelihood of knock will be increased though. More spark energy at low engine loads might actually hurt efficiency though, since the ignition timing here should already be tuned to achieve maximum brake torque with the recommended plugs.

Here's a figure from a study that compared traditional copper plugs (Type A), to a platinum/iridium (Type B), and a plug with three ground electrodes (Type C). With air fuel ratios near stoiciometric (1.0), there was no significant efficiency improvement, but the platinum/iridium type plug performed much better in very lean conditions.

View attachment 227037

Here's what the flame looks like for each plug. The iridium/platinum produced the fastest flame growth in lean conditions, but not significantly faster near stoichiometric AFRs. The three-electrode plug performed the worst, but its gap was smaller than the other two.

View attachment 227038

Great information, thanks for sharing. Could you link the study for further reading?

 

[Oillover]

Some vehicles are picky about plugs. Toyota only like Denso or NGK. Other vehicles will fire and run well with pretty much anything you can stuff in the hole. I always use whatever they came with originally .

Ed Zachary!

Back when Bosch launched the "platinum" plugs in the 90s, everyone thought they were the best plug for their Euro vehicle.
Our Volvo's ran terribly on them. They preferred the plain-jane copper plugs.
Another theory is that the regular fuel might have caused the running issues, but my dad wasn't one to spend more on something that's not necessary. So copper plugs and regular fuel seemed like the best mix for that old tractor

 

[Rmay635703]

Ed Zachary!

Back when Bosch launched the "platinum" plugs in the 90s, everyone thought they were the best plug for their Euro vehicle.
Our Volvo's ran terribly on them. They preferred the plain-jane copper plugs.
Another theory is that the regular fuel might have caused the running issues, but my dad wasn't one to spend more on something that's not necessary. So copper plugs and regular fuel seemed like the best mix for that old tractor

Plugs affect timing and the “heat” of the spark .

Modern cars adjust around it but others need a very narrow range of plug characteristics to not misfire.

Honda Insights are notoriously picky on plugs

 

[CarlB]

Plug indexing will also impact combustion, but for most use cases it doesn't make enough impact to merit the effort.

 

[burbguy82]

That isn't how it works.

The same amount of power (to charge the coil) will be used regardless of the resistance at the spark plug gap.

I was referring to the power required to make the spark.....the bigger the gap the more power required.

 

[twX]

Great information, thanks for sharing. Could you link the study for further reading?

Here's the study, SAE 2005-01-1133.

A couple of other good studies are SAE 2000-01-0960, and SAE 920413.

 

[PandaBear]

My observation is always that the sharper the tip the lower the spark voltage required to ignite the gas, and it is really the physics behind it. Platinum etc makes it easier to make a plug that last longer and therefore they can have a finer tip that last just the same, so it is easier to fire, and therefore less misfire. Some decided to do the trade off between tip size and plug gap, and go for a larger gap and smaller tip to make it ignite more gas at the same time (I never bother).

The only time I really try to look for a new plug is when I failed smog. I'll do everything to increase my odd of passing: new plug, 91 gas, Technron, new oxygen sensor, oil change, drive till the engine warm up, etc.

 

[Audioquest]

Stick with what's listed in the manual. Fine tip plugs (Plat, IR, Ruth) require less voltage to fire and work better with today's ignition coil packs.