Yep GTX is an old name that many non-oil people recognise, it’s the same here.My mom has a 04 Marquis with 150K miles on it that sits up in a garage in high humidity. I use Castrol Magnatec because it is cheap and a synthetic. Could easily run Chevron supreme (Good and low cost conventional) Super tech Syn, QSUD, or Havoline but my dad LOVED Castrol GTX. That's a brand my mom has seen through the years so she is comfortable with me dumping that in the engine.
For those people, who know GTX and ask me about which oil to get, I mostly suggest they step it up to Castrol Magnatec synthetic. A good oil, in a brand they know, that doesn’t break the bank.