Looking to get a car - pick up in Amsterdam (in the city, Amstel Business Park) and return in DUS (airport).

Planning to pick it up around closing time on 6/24 (5pm-6pm) and return on the 27th - planning to do it around 8pm.

Is there any way for me to do this with 3 days rental? Or not to worry about it and pay for 4 days? What happens if I say I return it by 6pm on the 28th, but actually get there at 8?

Also, if somebody can chime it with a way to get a better rate for a car with auto (yes, american way ) - I would appreciate it. Now I got 4 days @ € 29.26 + € 125 for one way + taxes/fees = € 302.55 for F (Golf or similar)