Your test was a hell of a lot more scientific than theirs if they actually used two different trucks.... I find it hard to believe that as far as they usually go to eliminate variables they would do something that stupid.... Did they even bother to run them side by side in same configuration first to check mileage against each other?

 

Ok this is gonna make me sound like a crazy ****.......oh wait I am, so I will go ahead and say it. My buddies dad has a 00 F150 sport, with a 4.6. He changed out the sparks to Bosch platinum +4's, and claims that he went from 15-17, to around 21 mpg, thats up to 5 mpg better. So if this is true (which knowing my freind it has to be) then it is plausible to get a little better gas mileage out of a 5.4. Since they dont make these plugs for the 05 5.4 Im am going to buy some denso Iridiums (when I have 150 to drop on them) and compare mileage to test this "theory" What do you guys think, myth or reality?

 

The ONLY way you could possibly see a large mpg gain from a spark plug swap is if something was wrong with the original set. If such a gain were seen then, it would have nothing to do with the brand that was installed, it was simply fixing something that was broken. Pretty much ANY healthy spark plug is fully capable of providing adequate spark under cruising conditions...

 

But platinum +4's have a platinum tip, and four firing posts (not sure of technical name) Which meens a hotter burn, so it clears out the cylinder faster, and burns all gas, instead of just partly, and then the partialy burnt gas is shoved out the exhaust pipe. Wouldnt that increase milieage (maybe not 5)? But like you it does confuse me how a clearing the cylinder out better could increase fuel mileage with the with the computer putiing the same amount of gas into the cylinder. Unless it makes the computer put less gas into the cylinder, in which you would see an increase.........I just confused myself! There is to much crap out there that supposedly increases fuel economy out there! Anyways not trying to disproove you roush, just trying to figure this out!

 

Sounds like their marketing department is doing a good job.....

As long as you have adequate spark there is little else to be done by a plug, especially under cruising conditions.

 

i had bocsh POS spark plugs in my truck for the 5,000 miles they worked and then i had a slight misfire then it got worse and worse pulled the plugs and 2 of them were dead! ive heard of someone running bocsh Plat 4's in his F-150 and the coil packs stoped working!!! and he replaced them twice before taking the bocshs out....Nothing but motorcraft will ever go on my truck again!!

 

It will only spark from the closest one, and they will not all be the same distance away from the center electrode. You should always check the gap of a plug when you change them, and if you have four electrodes you can't do this. Your truck has 02 sensors that monitor how your engine is running and will do a pretty good job of keeping it in spec by adjusting the fuel trim. If you have unburn fuel going into your exhaust you have a serious problem and will be melting the catalytic conver(s) down in a short period of time.

Boshe makes good plugs, just don't put them in Fords. Happy endings with that combination are few and far between.

Like the others said, if changing the plugs helps your milage it is because your old plugs were shot, not because they only had one electrode.