Odd Onan issue

I have a 5.5 onan 4 months old started good at dealer. got to the desert and ran for 3 hours then stopped. The gen is tested b4 release to the customer. BUT I was advised I had bad gas. replaced carb and drained out gas runs fine now, also if you have a fuel station have it drained to if you suspect bad gas. Use 91 octane use seafome run at least once a month for an hour at full load, two air conditions or etc