I am getting a Truvativ Styli 1.1 gxp SS crank for a build and noticed it recommend me to use a 3/32" 9-speed chain. I would have thought you would use a single speed chain on a single speed crank. Looking around at other cranks I have found that many of them also require or recommend narrow chains. For example:

Crank: Chain recommendations
Sram S300: 9 or 10 speed (even though "track" is stamped on the ring)
Sram S100: 3/32" chains
Truvativ Styli oct: 9-speed 3/32
Truvativ Descent: 9 or 10 speed 3/32
Truvativ HammerSchmidt: 9 speed 3/32
Sugino RD: 9-speed 3/32"
Sugino Messenger 3/32" or 1/8"

My LBS guy told me to use a ss chain as well even though the manufacturer tells me otherwise. Does anyone have the scoop on which to use and why? cause I am a little confused.
Thanks.

Recommending 9 or 10 speed chain on an SS crank? That's really goofy. With more speeds the chain gets narrower and wears significantly faster. Whatever you do, don't buy 9 or 10 speed chain unless you're running a 9/10s drivetrain. Just get 6/7/8s chain if you want to run 3/32

For SS/FG bikes, there are really only two chain widths to worry about: 1/8 and 3/32. You can run 1/8 chain on anything*, but you cannot run 3/32 chain on 1/8 chainrings or cogs.

*I recently discovered that I cannot use 1/8 chain with a Hyperglide cassette sprocket, but I can use multi-speed derailer chain on those same cogs. The combination of wider chain and littler teeth makes it derail any time I get up to any kind of speed, which was very frustrating until I replaced the cog with an SS unit and my problems vanished.

Thanks,
I was planning on using a wider chain until i saw the manf. recommendations for a 9 speed chain. Why would Sram/Truvativ (and others) recommend 9 speed 3/32" it if it is not as durable as a 6/7/8 or 1/8" chain? There must be something I'm missing. Less play in a narrower chain?

BTW my setup is a Truvativ Stylo 1.1 MTB SS crank with a Surly 18t cog which takes both chains I think.

I really have no idea. There's no functional reason you'd wanna run anything narrower than 6/7/8s on a single speed. The only thing I can think of is that it's a conspiracy to confuse, and to get people to buy more chains.

If you buy one of those 9/10s cranksets just get 6/7/8s chain, or even 1/8 chain if you want. It'll all work fine.