Hey guys changed out my plugs today, a real pain in the butt on the 3rd one back on the driver side and the last one back on the passenger side, the others were pretty easy but it still took me 3 hours roughly. Not to bad for first time doing it I guess.

Anyways the truck has 46k miles on er and had the original motorcraft plugs I think (I bought it at 11kmiles). When I got the old plugs out the base of them including around the electrode and the little metal tip were all slightly brown, like a light rusty color. Not sure if this is normal.

Also the ggap on them was about .070 to .075 and they all looked very eroded, the electrode was definatly very coned. I cant remember what the gap is suppose to be but it looked huge.

Put in the bausch ones with the four prongs around the electrode (forgot what they were called) and it seems to have restored some power back. I hope it puts some gas mileage back on also.

 

If you see increased MPG by changing the plugs, you'll be the first. You might get an increase of 0.25 MPG at best but not something you'll notice for sure. However you'll notice an increase in power, especially at full throttle.

I forget which auto magazine (maybe Motor Trend) it was but they tested multiple prong plugs recently and they made no difference, unless you expect to break off prongs on original plugs (which I've not seen except the time I blew a hole in a piston in my Chevy van and the same in my boat). I ran Bosch platinum when they first come out several decades ago but never notice any difference. The were single prongs and not even splitfires.

 

Yeah I have noticed a great improvment in power but that could be due to the fact that the others were so out of spec as far as gapwas concerned. I will report back on gas mileage allthough I do agree that it probably wont be much at all. I dont have the meter to show me gas mileage so I gotta do it the old fashioned way.

Still it got alot of its umpff back so thats good.

I dont think I have ever scene a plug lose a part before thats pretty impressive.

 

More umpff should equal a more efficient engine. You may see a little gain in mileage.

I have seen a plug come apart, a Bosch platinum (single electrode). The platinum fell out of the center of the plug and got caught between the piston and the cylinderwall and ruined a perfectly good 5.0 in my Dad's 89 F150. It only had 109K on it. After I pulled the engine due to it fouling that cylinders plug and puking oil into the air cleaner from blow-by, I found a nice deep gouge down the cylinderwall. I'll never use Bosch again. It's Motorcraft or Autolite for me.
This is my personal opinion, not the opinion of FTE but after having to replace the engine over a $3 part, I'll never use them again!!!

 

I used Denso Iriduims when I did my change. I also had a bad coil that I replaced at the same time. Same deal on the eroded plugs all between 0.068 and 0.075".

I took a long, 800 mile trip two days later. My previous best mileage was around 16 and on my trip I saw 19.4mpg. So it is possible to see improvement.

 

While I'd bet that your 3.4 mpg increase was more because of the coil and not so much because of plug replacement, with an increase of power you can see an increase of MPG. Usually though, when the extra power is noticed, drivers (including me) seem to use/abuse that extra power, negating any mpg gain. To see a mpg gain, you'll have to remove any lead in your foot.

 

It was probably the coil that made the biggest difference. However, I'll take it no matter what the cause.

My saying is fuel economy is a function of the right foot.

 

My right foot will never let me find out for sure.

 

Hence why I own a truck and not a mustang anymore. Jail cells look alot cooler from the outside.