Just choose the oil 20/50 till you will have this car.
However, as you said Havoline 20/50 was not good. I totally agree.
You can choose
ZIC Hi-Flow 20/50
Performa 20/50 => this is very good oil
SIL Motor Oil 20/50 => this is company from UAE. Not widely available, but its also very good oil.
Liqui Moly 20/50 (Check the exact name of their 20/50 oil for gasoline).
All the 20/50 oils need to be change after every 3 ~ 3.2K
But you should choose different companies oil every time and then decide by yourself that which company's oil gave you good mileage & keep engine cool.
Never use local companies like Castrol, Shell, Toyota, Guards, etc.
Trust imported companies like Performa, ZIC, Liqui Moly, SIL.
But do not change the viscosity and keep it 20/50.
All the best