Autolite spark plug issues?

[nunrleft]

About 20,000 miles ago I changed spark plugs because because of a significant misfire. Yesterday the same thing happened with a couple CEL codes of p0300 and p0306, (multiple misfires and misfire on #6 cylinder).

The plugs I previously put in were Autolite double platinum.

The new plugs I installed are Champion Iridium, which took care of the misfire completely.

Any thoughts as to why I got only 20,000 miles out of the Autolites?

60% of my driving is city.
I don't really tow anything
Synthetic oil changes every 4,000 miles
101,000 miles on the pickup
Bought the pickup with 70,000 miles on it. At 80,000 miles I installed a new Cam Position Sensor as the original one was squeaking badly.
New Autolite 2x platinums at 81,000.
Seafoam treatments through the master cylinder vacuum at 70,000 and 90,000.

 

[snoman6115]

for a ranger i was told to only use autolite, plus i HATE champions, i've never ahd luck with them in anything

 

[Psychopete]

70,000 - Truck just bought and seafoam
80,000 - Plugs replaced because of significant misfire
90,000 - Seafoamed
100,000 New Plugs because of misfire

I don't know if it's just me, but seems like there's a good pattern going on here. What did the plugs look like? Was it both the same cylinder that was misfiring, and was the cylinder that was mis-firing show any signs of oil or anything that shouldn't be there? A lot of people change plugs after seafoaming, IMO run the plugs (champion) for what they will live for, and I would recommend going with a set of Motorcrafts that are as close to OEM as possible - and go from there (without seafoaming ). Are you seafoaming to try and clean carbon to help resolve pinging?

Pete

 

[bigcountry]

you might want to check for a possible head gasket leak

 

[nunrleft]

Different cylinders each time. The first time was one on the passenger bank (I forget which cylinder). This time was the driver's side, rear (#6). All the plugs were whitish tan with a little crusty build up on them. No signs of oil or anything else.

The seafoam treatment I do as a preventative measure to help keep the EGR ports clean.

A head gasket leak should show other symptoms and the misfire wouldn't be solved by changing spark plugs, don't you think?