NGK 6481 ILFR6B iridium spark plugs. What lights your fire!?
Hey!... And welcome to another #modmonday! This week we are looking at the turbo Ej25's oem spark plug choice! Which is NGK ILFFR6B 6481 Iridium spark plugs, I have had many trouble free miles on both cars with these installed and continue to use them in both today.
Here they are in all their glory. Nothing too crazy but they get the job done properly! NGK ILFFR6B 6481 Iridium spark plugs
There are plenty of options out there by why stick with the factory NGKs? They were designed specifically by NGK for Subaru to highest of factory standards and to last 100k . Like many other iridium plugs it is pregapped and ready for installation, NGk recommends 18-21 ft lbs of torque for these in an aluminum.
Good looking plug! Nice tan area on the electrode and a bit of carbon on the threads and surrounding area. NGK ILFFR6B 6481 Iridium spark plugs
These will do well in a modified or stock Subaru. If you end up modifying your car to making more than 75-100 hp over stock you will need to look into colder plugs to keep up with the additional heat. Speak with your tuner for further specifics.
When you run to the local parts store or use their online search you may end up with a different spark plug number from Ngk. They generally have this spark plug in stock so they are happy to sell it to you. That NGK spark plug is the LFR6AIX which has many of the traits needed for your Subaru engine but is wrong in one area. The spark plug gap is .043"(1.1mm) vs the factory .031"(.8mm). While that doesn't see like much it is enough to cause a few issues.
Front is the OE spec and rear is the IX. Not too much much visually different between the two but a spark plug gaping tool will show you the gap is too wide.
I have actually regapped these plugs to the Oem spec .031" but still found that overtime they will expand to their typical size of .043". When I installed them I had a noticeable rougher idle but ran well. With that being said be wary of what the parts store or online retailers will sell you as a direct replacement.
Here are the two plugs side by side. Slight differences but easy to confuse the two. Always look for the blue text on your plug for the factory option.
After dealing with the above spark plugs I have stuck with the tried and true NGKs. I believe the Forester came with the incorrect plugs when I bought it, which is just another reason to replace them when you buy a new to you car. Keeping up on these maintenance items will help keep your Subaru running well for many miles!
Questions, comments, thoughts? Leave them below!
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NGK ILFFR6B 6481 Iridium spark plugs
Tekton spark plug socket 5/8th