Quicksilver 8M0046007 NGK TR5IX Iridium Spark Plug, 1-Pack

Great product. Great performance and easy to install, typical spark plug installation. Highly recommend. Were Installed in both my vehicles.

These replace the former NGK part TR55 iridium spark plugs. Not sure of what the difference is, but I suspect it is slight. Installed 8 of these gapped at 0.040" on a 2004 Pontiac GTO, along with 8.5mm MSD wires (generic LS1 kit) and K&N Cold Air Intake kit (57-3044). The car was formerly throwing engine codes of right and left banks running lean/rich. New plugs and wires cleared that code. I've read on forums that the TR5IX plugs show a 5HP gain over stock plugs if your car is already modded, but may be only as good as stock plugs if the car is stock otherwise. Car is perhaps a slight bit more responsive, but I think that is due to clearing the engine code and letting the engine relearn itself. Removing stock wires on an LS1 is a ridiculous job (you just have to rip them out), so that added time to the whole job. Plugs and wires took 3 hours (yes, I know, that is retarded long), but the new MSD wires have a much longer boot on them which will facilitate easy extraction - the stock boots are nearly buried in the LS1's plug head shields, so there's not much to grab. Changed mine at 80K miles. Seems to have helped the car overall, however no improvement in MPG. Worth the money if you're going to mod the car further, or just want to be able to say you have NGK iridium plugs (stocker AC Delco plugs are iridium as well). Overall, installing the plugs is easy as long as you have a spark plug socket with a universal joint. Recommended for every LS1 Goat.

If you have a GM vehicle with 0.060" gap plugs and you haven't made the change yet to smaller gap plugs, ~0.040", you are in for a real treat. My old Iridium plugs were set up at the stock 0.060" when they were installed and after 70k miles the gap had widened even further to about 0.080". I have a 2001 Tahoe, 5.3L V8. It is hilly where I live and the truck would frequently downshift. In fact, the motor ran exactly like it would if it was running on cheap gas. I just lived with it because I thought it was a result of our 5280 ft elevation and the 85 octane gas they call regular up here. Whoa was I surprised after I installed these new plugs! The biggest thing I noticed was an improvement in part throttle acceleration and engine smoothness when cruising at highway speeds. Downshifting has also been reduced dramatically up grades. Idle smoothness and full throttle acceleration are about the same which was pretty good before. If you are one of those guys who feels and hears every little nuance from your motor when driving you will really love these plugs with a smaller gap. Simply amazing difference. I haven't checked mileage yet because I'm sure it is worse right now....I haven't been able to keep my foot out of the pedal. This engine is running better than it ever has, even at 138k miles. Amazing.

I really enjoy having these plugs in my car. They have a high quality construction and went in nice and smooth. Out of the box, they were gapped slightly smaller than advertized, and they are a bit harder to set the gap on than regular plugs. Fortunately, the iridium center electrode that makes them harder to gap is what gives them their high performance, so I can live with that.

Replaced original plugs on 2009 Chevy Suburban Z71, 5.3L, 105,000 miles. Shipped fast and work fine. Put a little anti-seize on threads before screwing into engine.

I replace the OEM plugs on my 2004 GMC Sierra Denali. Most likely the last time I will need to change plugs. So far, great start, great acceleration and power.

got theses went to about 18 gillion mile. got them for a ford focus 2000 SE hatch back. should of never got these. before i replaced them i was getting closer to 28 miles to the gallon i did not change the wires tho. oh the gape was all wrong had to re gape each one. gape on my car is .050 my mechanical guy warned me to not get these i didn't listen i like to try new things to see yup these no good.

Item picture is misleading. This is for a single spark plug not a box of 4 as shown. Arrived quickly but will be sending back due to misleading advertisement.