Recommended Trans Fluid

I switched to Castrol Synthetic ATF shortly after getting my car but 8K later did another fluid change with Valvoline Synthetic ATF after reading either on this forum or Clubgp that Castrol was basically not "real" synthetic or something. The back of the Valvoline synthetic bottle says "GM-approved synthetic."

castrol recently went through some issues, and I believe were sold (they are now part of BP) first of the year they were not approved for use in GM vehicles