I actually went to my Mazda dealer and checked out this OEM
https://www.amazon.com/dp/ (commissions earned)https://www.amazon.com/dp/ (commissions earned)a couple of years ago. The description on the back does say GF-4. And the parts guy who has been working for this one of the oldest Mazda dealers in Dallas area all his life told me Mazda says it’s made by Castrol and it’s the same oil as GTX which is a conventional oil.
Here’s an example a CX-5 owner with 2.5T did an oil change at his Mazda dealer. The invoice says the oil used is Mazda OEM 0000-78-5W30-BK (bulk?) and the service claimed it’s full synthetic. After pushing for proof, the parts manager admitted it’s NOT full synthetic. Ended up the Mazda dealer not only replaced the OEM Mazda 5W-30 oil with full synthetic 5W-30 oil and a new OEM oil filter, but also gave him and his wife 3 free oil changes!
Mazda Moly Oil in 5W-30: Does It Even Exist?
So Mazda OEM 0000-78-5W30-BK oil which replaces 0000-77-5W30-BK oil which is the same Genuine Mazda SAE 5W-30 Super Premium Motor Oil 0000-77-5W30-QT in bottle, is still not full synthetic. I’ll never use an oil which is not full synthetic if I have a turbo. Have seen too many issues due to the extremely high temperature on turbo with conventional oils.