Autolite Iridium XP Automotive Replacement Spark Plug, XP103 (1 Pack)

Perfect fit and makes the truck run like a champ. I expect a noticeable improvement in gas mileage too -- time will tell.*March 12 2015 -- UPDATE: After nearly 10,000 miles with these plugs installed (and new wires & air filter) I have seen a 3MPG increase in fuel economy, and the engine stills runs smooth and quiet. Great plugs!

Plugs is plugs ... but now I know that's not the case. If you leave the plug choice to `least expensive', or your mechanic, you will likely see little change in vehicle performance. That's been my years of experience.I was intrigued by a scientific journal article that considered various `spark plug' designs in combustion system dynamics. From that curiosity, I went to looking for the `optimum' plug at the best price for my latest plug change. There are cheap, middle and premium plugs to be considered. If you are going to spend the time on the knuckle-busting job of changing the plugs, why not put the 'best' plugs in?Iridium plugs trump platinum plugs simply from iridium's place on the periodic chart of elements. I considered the `super-premium' plugs that incorporate mini-subsystems that can run up to $25 a pop. The high dollar, mini-system plugs incorporate inherently superior spark dynamics in the ignition cycle. But, on deeper consideration after checking the engine specs on-line... your vehicle's OEM computer will suppress these advantages in the 'greater' vehicle combustion optimization equation ... super-plugs require a super, non-OEM computer, to unlock the plugs capability. The high dollar, super-plug will be dumbed down by the OEM vehicle's computer.So, I went the middling route for my Lincoln Navigator by shifting my electrodes one element left in the periodic chart and looked for the least expensive plug in that category. I watch fuel consumption and was amazed that these plugs upped the mileage over 10%. There are just not that many ways to get a real 10% improvement in mileage.5-star ... the results exceeded my expectations. I received all 8 in one order. The odd-number purchase problem another reviewer provided must have been corrected.

Didn't do what it was advertised to do for my vehicle, 2003 Ford F-250, which has 14mm spark plug threads. In order to use the rethreader tool you need a 3/4" socket which is to wide in diameter to fix down into the spark plug hole. P/N OEMTOOLS 25647 Spark Plug Saver.

Been using Fram products for 45 YEARS. That should about say it all. Great product performance at a reasonable a price as is out there. I'll keep using them as long as I'm able to drive.

Quality Iridium Autolite Plugs with a good rebate deal on them right now. I would buy them again as they are one of the recommend Brands and Type of plugs for my car.

good working

I purchased these for a higher mileage vehicle to replace a set that was installed by a mechanic claimed were OEM plugs the last time my car hit the factory recommended mileage for a new set of plugs. Sadly they were not OEM but even cheaper and slightly incorrect but still functional. After putting these plugs in, it feels like the car is performing slightly better but I also did quite a bit more work replacing sensors and performing general maintenance so its hard to say overall. When I ordered Amazon was out so I got a few plugs from other sellers through Amazon - some plugs came in the proper packaging, some were simply shrink wrapped and I'm assuming where for mechanics. I'm confident in these plugs based on my research and they were the right price. It was only a 20% increase in over all cost for me to use these plugs vs. OEM plugs which is a solid bet towards a longer life of my engine especially when the life of most plugs are rated for an extreme number of miles.

Great price. Great performance. The plugs have helped with power and performance, MPG have improved and the engine runs very smooth now.