Civic VX spark plugs ZFR4F-11 ZFR5F-11
 

Honda recommend the Civic 92-95 VX to use spark plugs ZFR4F-11 and ZFR5F-11 in hot climate or continuous high speed driving.

Has anyone try using the heat range 5 yet in this hot summer climate? If not, I might be willing to try it once I get my mpguino installed.

I tried the ZFR5 in my 98 HX, not good, ZFR4 good.

Use the colder 4's. lean burn = less heat, so a hotter plug may misfire by not getting up to temp. If they made a 3, that might be worth trying, otherwise stay with the 4's.

I think you mean 4's are hotter. NGK lower number = hotter, higher number = colder.

Correct spark plugs for my VX
 

So I've been away for awhile struggling to resolve a sudden 10 mpg drop after a tune up. I will share more about Pearl's journey to 50 mpg, but...

Could the fives the dealer sold me account for that severe of a change?
I don't know have a record of the existing plugs that were replaced.
It would make me Very happy to solve this frustrating and expensive conundrum.

Are there also special ignition wires for VX?

From my understanding the plugs all moved 1 number higher to account for ethanol in gas.

I run autolite iridium 5244 plugs and I'm very happy with their performance

Zr5f are the recommended plug per the parts store. I have noticed that gap size decreases and heat range decreases with ethanol to make up for lack of combustion

And yes, ngk tr555 in the camaro for daily driver, ngk tr6 for nitrous. Higher number is colder

Zfr5f or 4?
 

The dealer i just talked to said both of these plugs (zfr5f & zfr4f) are ngk iridium and that they are the exact same plug other than the stamp.
I am trying to re-gain 10 mpg lost after a tune by a guy unfamilar with the special nature of the VX.
I also have a 97 HX to double check.

You better check around because those numbers do not match any ngk iridium plugs that I could find. Those are standard plugs, not iridium, they are copper core. I have an HX and that's what I run. The cost about 12.00 for 4 and you would never get iridium for that. The ngk numbers 4 & 5 are heat ranges 5 being the colder plug, 4's best for lean burn.

Tune? There is no such thing. you mean tune up?

Both plugs are copper core but the plug looks polished like a platinum plug but the core is copper

Thanks you're right, they are indeed Not iridium tipped (the dealer was wrong-surprise).
They are copper and nickel tipped according to the ngk website.
I actually have the 4's.
If there's an actual mpg increase in an ngk iridium, please recommend. Otherwise, I will keep these in the VX & HX too.
No such thing as a tune? Ok fine. :) I didn't proof my work.

I can not verify any claims of increased fuel economy with iridium plugs as they were one of my first replacements when I got the car.

My theory was the more concentrated spark from the iridium tip would benefit the combustion time as the spark arcs more quickly.

But no, technically the only difference is an iridium tip will not degrade as quickly over time like a copper tip. So the only benefit is longer plug life

I recommend to all my customers go with factory. I felt like splurging and didn't have the 4f plugs in stock, no complaints from iridiums and my fuel logs are extremely consistent.