Do valve guide seals go bad?

[Mike W.]

My '03 Q, with the 3.5 engine has an increasing appetite for oil. 5 quarts on a 4300 mile vacation and it shows at the bottom of the hash marks now. Now I strongly suspect it needs an engine or rebuild. It sends up a smokescreen the first start of the day at times, which is typically a sign of VG seals. But I fear the worst. 168K on it. Anyone know what they were made of, neoprene, Viton, ???

[mdmellott]

I can't say for certain what Nissan/Infiniti OEM used in their seals. According to napaonline.com, "valve stem seals are made from a variety of materials, including nylon, PTFE rubber, steel, and synthetic rubber. Sometimes these materials are combined into a single sophisticated design. When synthetic rubber is used, there are three basic types: nitrile, polyacrylate, and Viton." https://knowhow.napaonline.com/what-are ... ur-engine/