Relating to this machine but off-topic... Is it ok to run Synthetic 5w-30 in this? It's not shown as an option on the manual but the machine is very old. Only reason I ask is that none of the oils shown really offer the range I think is appropriate for a generator. The owner uses it as back up so odds are, it's going to be very hot or very cold out when he needs it. A nice range of temperature would be ideal. The best listed in the manual would be 10w-30 or 10w-40. Both show they are good from 0-80 degrees.
My auto mechanic puts synthetic 5w-30 in all of his small equipment and always recommends it for that purpose. But then again, he sends his small equipment to me.
Thanks.