Civic VX spark plugs ZFR4F-11 ZFR5F-11

[Chrysler kid]

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.