When it comes to Car Rentals, Priceline has always trumped all these coupon combinations from the Dealer direct.
Right now I'm searching for a 1 month rental March 20- April 17 from Chicago. All Hertz codes are useless except the CDP one. Combining codes (CDP, Xq, rzasjdb, blah!) just brings the price up!?
Also, be aware airports usually charge ridonkulous fees & taxes. Chicago MDW dealers for some reason lower their daily rental prices to somewhat balance that end price difference.
All in all.
Hertz with codes about 19/day + tax
Priceline 14/day + tax
... Trying to negotiate for less, but they won't budge
OH! If you're UNDER 24, Hertz has a really legit sale rate for you, works out better than most. My friend just booked it.