Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
If EWR does end up being the cheapest, price the rental with an EWR pick-up, and a Manhattan return: it may cost no more. Also look at doing the same with Budget, instead of Avis. And if you will be renting with some frequency, Budget currently has a promotion for its FastBreak members (enrollment is free) that provides for a $25-off coupon after every two rentals of two days or more. (Check the promotion details to make sure that the coupon is valid for use in the NYC metro area.)