Oil in spark plug tubes?

[Paul]

Originally Posted by magno_grail

Had the same problem on my friend's '98. The O-rings deteriorate eventually. You can buy a pair from the usual sources or a lifetime supply for about the same cost from McMaster. Large are -320 Silicone, small are -121 Silicone

Thanks for the lead. Is this the correct part for the larger one? (-320)

High-Temperature Silicone O-Rings

These silicone O-rings withstand temperatures up to 450° F. They have a round profile and are suitable for a wide range of static and dynamic sealing applications. All include material certification with shelf life, cure date, and traceable lot number.

Inch O-rings have a dash number and are sized to the SAE standard AS568.
Inch

Fractional

Actual

Dash
Number ID OD ID OD Hardness Specifications Met Temperature
Range, °F Color Pkg.
Qty. Pkg.
Wd.: 3/16 Fractional (0.210" Actual)
320 1 1/8 1 1/2 1.100" 1.520" Durometer 70A (Medium) Made of FDA Listed Material, SAE AS568, SAE J200 -80° to 450° Red 10 1283N263 $6.62

https://www.mcmaster.com/#silicone-o-rings/=17cerk6