The Roav Power Washer works great... I used it to wash my car last week! Side note: if you're using the soap dispenser, be sure to dilute your car wash solution with water or your car will get lost in all the suds!
It also works great for doing the siding of my house, but one thing to note is that it wasn't quite strong enough to reach all areas of the seconds floor from the ground. So you may need to get the ladder out if you have a two story home.