2008 fx4 5.4 Most auto website say my truck takes motorcraft sp 515 spark plugs. Even autozone.So I ordered some . So tonight I wanted to do the tune up but the plugs in my truck are Motorcraft SP 509. So what plugs do I use? The 515 will sit further in the motor.

 

If i can use either plug which plug is better? One burn hotter?

 

If you don't have any history on the truck I would use what you took out if you weren't having any problems.

 

You must have a 08 with the redesigned heads. The SP 515 won't work in your truck, those are for the ones pre 10/07 built. The SP 509 is the right plug.

 

Thanks otto!