I usually just drive over to Costco and combine it with a grocery run, but you do need to be a member to use it (don’t know if you are). I know there’s a car wash at the gas station at California & Admiral, but haven’t used it, so don’t know if it’s any good.
Costco when it is just the exterior, Elephant after the dogs have been inside the truck, cuz they vacuum out all the long dog hairs, sand and dirt. ;-)
I totally spaced on the 35th carwash (close to 25th and Morgan/Sylvan.) It’s good, not as cheap as the Burien one, but probably the same price when gas is figured in.