Spark plug for Gasoline version of engine vs Flex-Fuel version

Snagglefoot

Snagglefoot

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I was checking out plugs for my Ford Taurus with a 3.0 OHV Vulcan engine. It’s an interesting engine because it has a waste spark ignition, but it’s not the waste spark I want to discuss. This car also came as a flex fuel or strictly gas engine. Here’s a question for owners of flex fuel vehicles ( not me). Most flex fuel ready vehicles do not burn flex fuel because of availability and other preferences. Yet, you can buy a spark plug for the flex fuel version or the gas version. Once your original plugs are done, and you are only burning gas, why would you want a plug dedicated to flex fuel?

The plugs recommended by Rock Auto are the NGK 5598 for flex fuel and the NGK 6579 for gas. Further to that I believe the plugs are same plug with a different gap. The flex fuel version is opened up a bit more. I don’t really trust the photos so I won’t post them. Thoughts?
 
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One may have a hotter heat range than the other.
I also assume that when you refer to "flex fuel" you are talking about E85, correct?
 
Are the fuel injectors different on the flex fuel version? I assume they must be. I wonder if that has anything to do with it.
 
Snagglefoot said:
I was checking out plugs for my Ford Taurus with a 3.0 OHV Vulcan engine. It’s an interesting engine because it has a waste spark ignition, but it’s not the waste spark I want to discuss. This car also came as a flex fuel or strictly gas engine. Here’s a question for owners of flex fuel vehicles. Most flex fuel ready vehicles do not burn flex fuel because of availability and other preferences. Yet, you can buy a spark plug for the flex fuel version or the gas version. Once your original plugs are done, and you are only burning gas, why would you want a plug dedicated to flex fuel?

The plugs recommended by Rock Auto are the NGK 5598 for flex fuel and the NGK 6579 for gas. Further to that I believe the plugs are same plug with a different gap. The flex fuel version is opened up a bit more. I don’t really trust the photos so I won’t post them. Thoughts?
Click to expand...
I asked Copilot about this... Here is what I asked it.

  • why are flex fuel spark plugs different than regular gasoline spark plugs? An example is, the plugs recommended by Rock Auto are the NGK 5598 for flex fuel and the NGK 6579 for gas. This is for a Ford Taurus 3.0 OHV

It had several reasons. I will not copy and paste but here is the summary. There was a decent amount of detail under each of these points.
  • E85 burns cooler—but requires more spark energy
  • Ethanol is more corrosive than gasoline
  • Ethanol often needs tighter or different gapping
  • Flex‑fuel engines run richer
 
Snagglefoot said:
Oh well. We aren’t supposed to post stuff directly but it’s a place to start I guess.
Click to expand...
That's why I sumarized what it said.

FWIW, I find AI very helpful. It needs to be vetted, but what it suggested in this instance seemed more than reasonable.

I suppose when the encyclopedia Britanica was invented people didn't trust those either... :ROFLMAO:
 
There is some truth that non-gasoline fuels are harder to ignite. Nitro- and methanol powered dragsters come to mind; they have impressive ignition systems.

A wider gap is generally better if the coils and everything else can support it. If you switch your car from points to HEI it's a good idea to go from 0.028" to 0.045" or maybe more, for example. Wider gap= bigger spark, more likely to catch some gasoline molecules and set them off at the right time.

When you gap your plugs during a tune-up, you're going to the thin side of perfect; they're allowed to grow gaps while in service. This was more of a thing with copper plugs that actually grew, of course. If your plugs were rated to 30k miles and you pull them every 5k and re-gap to what the manual says, you're actually doing a disservice.
 
Based on the above, if you had a flex fuel ready engine but was only buying gasoline, when it came time to change the plugs would you try outsmart the engineers and change the plug to the 6579, which is the one for the gasoline version. You could always examine a plug and try decide if a hotter plug would do some good.
 
Snagglefoot said:
Let’s just say if the oil price remains higher for longer than the “ experts” say, do you think E85 might see growth?
Click to expand...
it is possible. We use it in the wife's 2014 T&C. I paid $2.239 yesterday for E85. Regular 87 E10 was $3.039. At this price E85 is 73.7% of the cost of the E10. I track my mileage every time in the Fuelly app and I do not see a drop in mileage that matches the price diffirential, so for me it makes sense.

Couple that with the Hy-Vee fuel saver program here in the Midwest and my 20 gallons of E85 cost me $4.98 total! That is a win.
 
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