Crater Lake

138 is certainly doable. Once you enter the park the road is narrow so plan to drive straight through to the campground. Roadside parking for a RV is limited.

Also, is you're not aware, there has been some fire activity in that area so you might encounter smoke. Here's the park's web site so keep up-to-date with the 'Alerts' given on the top of the page.

Crater Lake National Park

I believe the NORTH entrance is still CLOSED....Dennis

According to the park's web site, the north entrance is now open.

230 and 138 are open right now unless the fire changes direction. 138 is ok for towing on.

Hwy 138 from Hwy 97 west is mostly straight and very easy grade. From the North entrance of the park to the rim drive is the best of the two routes to the rim, much easier and closer the the south entrance from the Bend area. It would probably be best to park the trailer before driving the rim drive. Crater Lake is one of my all time favorite places, I grew up along Hwy 138 and the lake was almost part of my back yard, had the pleasure of visiting and working there many times. Enjoy!