Anyone know which company has the cheapest/best fuel mileage car for rent right now?

Need to drive my father out to Denver (~2200 miles) to see his sister who isn't in the best of health at the moment...

TIA!

-Justin

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-Justin

91 560 SEC AMG - other dogs dd
01 Honda S2000 - dogs dd
07 MB ML320 CDI - dd
16 Lexus IS250 - wifes dd

it's automatic.