Will likely work just fine.

The FSA cranksets I have are marked 9/10 compatible.

 

A 9-spd chain will work very well on an 8-spd drivetrain. Better than an 8-spd chain in my experience.

Better shifting and quieter.

 

Sure, no trouble at all.

 

Any crank will work fine - 9, 10, or 11. I'd stick with 8 speed chains because they are tough and cheaper and work fine with those cranks. KMC comes to mind.

 

If the crank is 10v, an 8v chain might rub in the crosses earlier, and could potentially shift just a little wonky. They tend to run the rings on a 10v crank a little bit closer.

But since there's no problem running a 10v chain on an 8v rear (I'm currently running one on a 6v freewheel, for reasons not worth mentioning) you have no problems.

 

8 speed chains have more internal bearing surface to their rollers so they last longer, as well as being 1/3 the price of a 10 speed chain. And many ten speed cranks are spaced the same as older cranks to increase chain crossover clearance.

"Might rub", not "does rub". My experience is that 8 speed chains don't rub any more than anything else, so I'm not sure why we need to worry the OP with a theoretical rubbing concern while encouraging someone with a Sora bike budget to buy expensive, shorter lived chains.

Especially when the added "rub" an 8 speed chain has over a 10 is .5mm, or less than the variance in cassette location from one brand of freehub to another, or the amount that any two frame's chainlines might vary.

 

I have found that drivetrain on bikes seem to be accommodating. I have a 9speed cassette, an 8 speed crank, and 10 speed chain and it cycles through the gears smooth as butter. I understand the 8,9 is compatible and I came across a new KMC 10 spd chain real cheap when I needed a new chain and thought I'd try it. It worked so I haven't taken it off.

 

I wore out the middle ring on one of my commuters. Its 8-speed Sora crank now has a 10-speed 105 middle ring. Everything else remains 8-speed. No problems.

 

Thanks for all of the great feedback. It seems like the best option would be to purchase the crank and then measure and compare with the current one. This way I can choose the best chain for the situation.

Knowing that folks here have had success with similar mixed systems makes me more confident in going ahead with the purchase.

Thanks again!