Spark plug threads/collar covered in oil, but not electrode

Bill Cool

Previously 87MustangGT
Founding Member
Nov 18, 1999
1,268
3
39
Seymour, CT
Short version: car was parked for five years. Just took her out of storage, drove for about 15 miles, then did a tune up. On the #4, 7, and 8 spark plugs, the collars (between the nut and the threads) and threads had oil on them. No oil on the electrodes.

I haven't changed the PCV or screen yet. Some of the valve cover bolts were loose when I checked them.

Yesterday, in the pouring rain, I was changing the coolant, and let the car run for 10 minutes at a time just parked in the driveway. The passenger side tailpipe had a little white smoke coming out; I just attributed this to the differential in temperature between the exhaust and the ambient air...but some research on this oiled plug issue suggests the "smoke" might be related? Only blue smoke is oil-related though, right?

Car has ~ 128k miles, with GT-40P heads that have 20K from ME on them, nevermind whatever the P.O. put on them.

An oiled plug on the left, a dry plug on the right. Both are the old ones, with white electrodes...
View attachment 207673
 
Maybe you burned the oil off the tips by letting it run?

If that was the case, how would plugs ever get oil fouled if running the engine burned the oil off? Regardless, my question was more how did the oil get there, than why was there oil just on the collar and not the electrode.

5L5, I'm hoping that's just it. I tightened the VC bolts I could get to w/o removing the upper intake; I'll pull the plugs after a couple more trips (and a new PCV) to see if the oil has returned...if so, I'll pull the upper and tighten all the bolts.
 
My VCs were leaking and I had a few plugs with oil on the collars. You should be able to tell where the oil has run down the head though. So if there's no evidence of the oil dripping down to the plugs, maybe take a look elsewhere?
 
ACS - the car sat for 5 years, the engine compartment was covered with grime. I wiped a ton of it away before finding this problem, so I wouldn't be able to find oil dripping :-/