Depends on how far you go between fill ups and which way you go. I know there's stations in Newport that will handle your rig.
Probably something in Philomath if you come across Hwy 20. Nothing easy on 99W in Corvallis without looping south a mile or so on 99W first. Monmouth maybe.
If you come across Hwy 22 and turn onto 99W, McMinnville & Newburg are likely to have something that will handle your rig. Might be something in Dallas, too, but that's a detour just before you get to 22.
If you go up the coast to Astoria I'm sure you'll find something along the way; Tillamook will have a station for sure. Might be something in Seaside, should be something in Astoria on your way to Portland along the river.