Visible marking of overhead cams to be expected?

[jthorner]

Our '96 Volvo 850 has a nice large oil fill cap through which one gets a good close up view of two of the camshaft lobes. Recently while changing the oil (at 100,250 miles total) I noticed that I can clearly see wear marks on these lobes. Nothing extreme, but still quite visible. Volvo recommends 12 month/10,000 mile oil changes on dino oil. I've always done a 6 month/5,000 mile OCI using either Mobil 1 or Castrol Syntec, typically in 10W-30 weight. Next time around I will get an oil analysis to see where the wear metals are running. I suppose that some visible wear is to be expected after 100,000 miles of use. Do you agree or disagree? Fuel economy is still excellent and a recent California rolling road emissions test passed, so I figure that the engine is still in good running condition. John

 

[Nosmo King]

I think what you are seeing is just a polishing of the lobes, not wear. The overhead cams with the bucket style cam follower is very gentle on the cams and there is usually lots of oil up there. Nothing to worry about, unless they are flat and if that was the case you would have extreme lifter noise.

 

[AV8R]

Cam nose wear is pretty dramatic. The lobes can look like they were plowed. I tend to go with the polishing theory, as long as you cannot feel any roughness on the noses with your fingernail. One of the problems with ohc designs is that the cams run too cool, leading to increased condensation on the lobes and consequent corrosive wear. I like to use high-TBN oils with a lot of ZDDP for ohc engines for this reason. HDEOs seem to do quite well, in my experience.