Car rental rates, like airline rates, change day to day. For an advertised rate, the offer code locks in that consistent rate at participating locations – it's a rate that won't change regardless of any fluctuations in the car rental market that may push rates above or below the advertised rate but have limited availability. Despite the advertised rate that your discount is set to deliver, budget.com will always present either the advertised rate (if your rental meets all terms and conditions) or the regular budget.com rate, whichever is lower.