We had an economy PT Cruiser. It was very drivable...not the best mileage (about 20 MPG), but because we were only driving less than 500 miles...we didn't take the hybrid that was offered (as an upgrade @ 10.00 per day). I saved money.
Wish I'd thought to look, and/or that they'd offered us this - we put 2300 miles on the PT Cruiser in 17 days! - so that was the downside: the $30/day we spent on gas fill-ups. We had booked the compact instead of the economy, I think they were priced the same, and my regret at the time was not taking the economy - which sounds like might have still been the PT cruiser.
But the rental rates at the moment for Seattle (and this was early August) were $79/wk as opposed to over $200/wk quoted by other companies. Fox's rates really jumped around *a lot* depending on the day I looked - so we did good by locking into something so low. No prepayment for your reservation, no credit card # needed - so if you see a great rate, nothing to lose by reserving it. Just print out your reservation and make sure your contract at the desk is the same.
One other mention: we needed a car to take to Canada on the ferry. Fox's rental agreements restrict you to certain US states only. But in fact they don't - that's only for their extra insurance if you purchase it - and they initialed our contract agreement saying Canada was OK. (I had first confirmed that we were covered insurance-wise in Canada, between our credit card for the car, and our own auto insurance for liability).
Edited to add: the on-line rates aren't an estimate if you reserve - it's a guarantee and you don't have to prepay - except don't include extras such as more insurance, or paying for their gasoline - which they did push hard for, but would have been a mistake.