Spark plug problems

I changed out my spark plugs the other day and they were gapped correctly and tightened down and everything seems to be correctly hooked up and back in place, but my gas mileage since changing them has dropped almost 5 mpg. Any suggestions what this could be? I didn't know if it was possible to just have a bad spark plug, and if so what i could do to figure out which one. Any help is greatly appreciated.

 

I used the OEM denso plugs. Bought them at the dealership. My truck is an 06 double cab trd. I had gotten about 17-18 mpg, but only ran a half a tank through it this time and noticed that the fuel gauge was going quicker than normal, filled up and got just over 12 mpg. Don't have any mods that should affect it. I guess I may just take them all out again and double check everything.

 

Tacoman,

Did taking it apart and fixing it help? I have the exact problem. After searching the threads this is the only one I could find.

Thanks

 

I had the same problem , but it only occurred for the first tank if gas after the plug change , then went back to normal .

 

2009 thread revival...

 

great, thanks. Hopefully after the next tank it will return to normal. I will update if it does.

Revived threads sometimes help!

 

My bad, I misread yours about having the same issue

 

Gestapo

 

Thats policia to you