My experience (posted somwhere else too):Most spark plugs seal to the cylinder head with a hollow metal washer which is crushed slightly between the flat surface of the head and that of the plug, just above the threads. If the torque used to install the plugs is not excessive, the washer can be reused when the plug is removed and reinserted, although this practice is, strictly speaking, not recommended and replacement washers are available.
Ford engines, however, were once distinct in using a tapered hole and a matching taper on the bottom of the plug above the threads, in order to seal the plug. The torque for installing and removing these plugs was higher and it was easier to break them if the wrench was applied partially off axis.
More recently, some types of Ford Fiesta, and Ka also had a similar sealing system. The torque required to install these plugs is less than with the above type, and it is extremely critical that they not be overtightened, since overtightening can result in it being difficult or impossible to remove them. In addition, they have been known to corrode into the cylinder head, particularly if left in too long between removals. In such a situation, it is not unknown for a plug to snap below the hexagonal nut, leaving just the threaded portion (and the outer electrode) in the cylinder head. Ford has on occasion issued TSB reminding technicians to use the correct methods of installation
What SoNiC said. You do the plugs in these cars sooner than 100K not because the plugs wear out but because they will get stuck in the engine if you don't loosen them.wow...
what is regaping spark plugs and how you do it ?
I agree. Long lasting, double platinum spark plugs are a blessing and a curse. If left untouched for 10 years, they may freeze in the threads.Ford design of the spark plugs is prone to seizing the plugs in the block. The more time you let them in, the harder is to get them out.........................
I replaced my plugs, '01 with 111K and they were a bit tight. I was particularly careful to not pull too hard on the flex handle. They were tight all the way out due to crud in the threads. Back bank about .068" and fronts .058". Otherwise all looked clean and all the same on the insulator near the tip. Single platinum factory issue, day one. The back bank small wire tips were about gone. Thanks to reverse polarity on the coil pack back bank. DOHC engine.I agree. Long lasting, double platinum spark plugs are a blessing and a curse. If left untouched for 10 years, they may freeze in the threads.
Long lasting antifreeze is the same. It's a blessing because I don't have to replace it for years. But it makes me not check coolant level and a leak can go undetected for a long time.