No. It is not illegal to pump your own gas in Oregon, although this is a relatively new law. In 2023, the Oregon legislature passed two bills into law that changed the way Oregonians and visitors pump gas. In rural counties, gas stations may offer self-serve gas at all hours. In non-rural counties gas stations must offer attended service, but they may also offer self-serve gas at no more than half of their pumps during operating hours. Signage is provided so customers can identify which pumps are self-service or attended service and you’ll pay the same price whichever way you choose to pump.
I hope that helps answer your question!