The example was just to demonstrate the scale of how much more expensive National quotes come out for me.
I rent cars a lot and have tried many combinations of codes, pick up day, how far in advance I reserve, etc. I currently use Hertz and have learned the best times to book to get the lowest rates.
A friend has been praising the Emerald Aisle and I would try it, but only if I can figure out how to get their pricing competitive with what I'm paying now. I guess I'm trying to establish whether National are just more expensive, or whether I'm doing it wrong.
If anyone wants to replicate my example search, it was at DTW from 1/28 (noon) to 2/4 (noon).