Went there for an oil change today. I bought a car at a Carmax in California and for ease of warranty-maintenance have always had oil changes, etc. done at a Carmax.
The oil change took an hour and 45 minutes because they didn't have a part or tool that they needed. Carmax lets you know up front an hour wait's normal. This is no Jiffy Lube. However, an hour and 45 minutes is a bit long and would merit a mere two stars.
The third star is for the car wash that was a benny with the oil change. Maybe other places give car washes too. The California Carmaxs sometimes give car washes, sometimes not. So I don't know the reasoning behind the washes. But it made me feel better because the car had really needed it and I'd been debating whether I wanted to do it myself or take it somewhere to get it done.
The plus side of an oil change at Carmax - they're trustworthy. Staff seems to really care about the Carmax reputation. I've had some good experiences at Jiffy Lubes and some not so good experiences.
The downside of an oil change at Carmax will definitely be the wait. Even if they have all the parts/tools they need, an hour's a long time. And they're really too far from anything for you to walk in the heat to one of the Tolleson shops/mall areas. Carmax has vending machines, coffee, water, and a TV the staff said is auto-programed to one station and cannot be changed. Fortunately, Ellen was on and I had a book to read.
If you decide trustworthiness outweighs speediness, give them a chance and bring a book.