re: Advice on renting a car to drop off in another location

Made this same trip four summers ago (Seattle/Denver) and used a company called Drive Away Holidays (found on Trip Advisor) who actually booked us through Hertz. Can't remember total charges but went with them after thoroughly researching every cost cutting option. Definitely no mileage charge and we saved appx $500 on the one-way fee. Of course this was a while back, good luck! Fantastic trip, btw!