We have found that there is wide variation in the prices charged by rental car companies.  The best way I have found is to check the rates of the following 5 companies through their 800 numbers.  When you find the best rate of these five reserve your car at that rate, then about 1-3 days or so before you are going to Maui go to Priceline.com and bid on a car at a rate that is several dollars below your reserved rate.  I have been able to get a lower rate at least half the time by doing this as long as you pick up and return your car to the same location and your stay is for 28 days or less.  The five companies are:

1. Alamo 1-800-327-9633

2. Budget  1-800-527-0700

3. National 1-800-227-7368

4. Advantage 1-800-777-5500 

5. Thrifty  1-800-847-4389