I have rented from sixt all over europe and the middle east. The sixt team at rejkyavik was the best i have used to date. Normally, i decline the insurance (because credit card picks it up) and the unlimited mileage option but i opted for both based on the sixt representative’s recommendations. I am SO GLAD i did! It was more peace of mind with insurance for the harsh roads and snowy conditions but also i easily exceeded the 500 km limit. Do yourself a favor and do both. Also, they upgraded me to a four wheel drive and free tank of gas at no additional cost. These guys were great!!