Yes, you can if you follow these instructions.  (The document has instructions for the original Onan 2800 generator in the Travato.  There are some differences for the new “quiet” Onan 2800i, introduced late in the 2021 model year.)

Travato Generator Oil Change

NOTE:   In 2021 Cummins updated their oil viscosity recommendations so that 10W30 (with a lightly larger operating range) is recommended for gas and lp generators and 10w40 for diesels.   10w30 is generally easier to find.