Well I just bought a set of the 3923 plugs and hope to get them in this weekend. Just wanted to know if anyone who has them noticed any better gas mileage after installing them.

 

You probably won't notice much of a difference with 3923's, because they're one step colder and a bit shorter than stock. The "benefit" of using these plugs is helping prevent detonation - the 5.2L/5.9L engines tend to detonate easily.

 

you will notice a difference off the bat with these plugs. being one step colder makes the truck run smoother. and yes i saw an increase in mileage

 

Way smoother idle and smother acceleration.

 

I saw better mileage right away with the 3922 (for the HO). I wish I has done it way earlier! General mileage went from 14 to 16...

 

My mileage hasn't changed too much but the truck definitely runs smoother (4.7l non-HO)

 

Just picked up 8 of these today myself for the '06 4.7, hope my fuel mileage gets better, distributorship installed 8 new fact spec plugs4 weeks ago (free since they did not do the 35K service before selling the vehilce, but doubt they did the rear diff or auto trans fluid, so still got that to look forward to), mileage DROPPED from 15 mpg intown to 12 MPG (last fill-up yesterday) and the idle was even rougher (hard to believe) than it was when I took it in (and they told me that was just the way they idled (liars)). Will let you know as well later how she went (please god, please give me the 3 mpg back lol).

Darrell

 

i just checked the autolite website and it shows the 3923s as being for the v6 and 3922 for the v8 but when i check some of the other sparkplug posts it seems some are using the v6 plugs in the v8 is there a reason for this

 

I got the 3923's based on good reviews by others here, mainly superdak's reccomendation.

 

I read on a web site called v8performance.com/tipsandtricks.htm that the 4.7L V8 runs better with the autolite 3923's and also gives you 4 to 5 more horsepower.