Another random point of reference:

- I have never gotten a midsize or standard car with Neverlost.

- I get Tauruses with NL about a third of the time. This is my most common rental: booked midsize/standard; I show up and there is a Taurus in my stall. It's a very common upgrade for 5*/PC midsize bookings.

- On those less-common occasions where I get a whopper upgrade to a premium/luxury/prestige car, there is nearly always a NL unit in the car.

Conclusion: bigger/fancier the car, better chance you will get Neverlost. If I were you, I would probably retain my compact booking at the great rate, and make sure to throw a decent map in your luggage. (Don't rely on the one-pager that Hertz gives you.)