IMHO, FS is as good as Quaker State Conventional or Pennzoil Conventional and is probably an upgrade over Valvoline conventional.
I'd use it without hesitation and I have.
I got the FS I have in my stash for $1.69/qt, but then I'm talking USD in the US which does make a difference.
If the price makes sense to you, buy it and use it.
OTOH, if Valvoline conventional is a better deal, I'd be happy using that as well although it does have an entirely different add pack.