I'm having problems getting down my rental car to $30/day or lower, including taxes and fees. Or maybe it's just a DTW and PHL problem, where I am renting.

So far I have tried:
- Autoslash, best I got was about $40/day
- National with corporate codes, also about $40/day (the contracted rates are $30/day but taxes increases them)
- Off-airport locations are slightly cheaper, but the costs of transportation/uber to these off-site locations make it a wash.

Are there strategies that I am not using? I can't justify paying $160 for a 4-day rental!!!