A few months back, I had an "incident" where one of my sparkplugs was lose enough that it caused a literal meltdown of one of the ignition coils on the passanger side - caused by the PO overtorquing the plug, stripping the thread.

So, I repaired with Sav-A-Thread (worked great), changed plugs, etc.

I also recently had the "opportunity" to change the valve cover gaskets (due to a leak from the sparkplug opening). The valve cover gasket repair kit from Fel-Pro is great, and includes 6 donuts for the spark-plug seals, along with the actual valve cover gaskets.

So, as I was changing the driver's side, I noticed that 2 of 3 plugs were seriously lose. Like 2 turns and they were out!!! The threads were fine.
The old plugs were Bosch 2+ (damn PO ).

Installed new Denso's, with a fuel economy imrovement over 3000 miles = 1.2mpg.

The lesson, check your plugs at each oil change!!!

 

will do in about 500miles from now