Just use what manual recommends.
My clone manual states 10w30 and 5w30 in freezing temperatures. It doesn't mention detergent oil, but it should be used.
For the record, I use SAE 30 detergent (20 in winter) in all my 4 cycles.
Some engine manufacturers specifically state not to use 10w40 for reasons to complex to get into here.
They have a tendency to coke up internals.