I brought my Carmax car to a mechanic immediately after purchase to get it checked out - they said the motor mounts were bad as were the front struts and needed to be replaced, along with a few other things. When I told the charmax folks this, they said there was no problem - I told them I'd give the car back, then, at which point they offered to change the front struts.
Almost exactly one month passed, and with normal driving the motor mounts broke down. Carmax replaced them under my warranty.
Carmax is better than any other used car dealer but be savvy and dont take their word for it.
PROS: No hassling, no haggling
CONS: You must still be a conscious consumer
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