I have not had problems with mine. It's a 2008. I will say that the all-city gas mileage is not great, around 20 to 22 mpg.
I had code P0128 occur and, rather than call for a new engine temperature sensor, it required a new thermostat. It only happened in the winter. The code is gone as a result of a great mechanic fixing it and gas mileage improved a little bit. The temp gauge was reading at 3/8 of the way up, or a little less. After the fix, it was reading a little more than 3/8 of the way up. I'm figuring it makes for a more complete fuel burn if it's running a tad hotter.
Mixed driving gets me 24 to 25 mpg. A highway jaunt where I vary the speed, down to the 55 and up to 70, and encounter some stop and go, gets me about 27 mpg. Just recently, I did some pure highway jaunts (basically open highway of at least 100 miles ... and gas station pump to gas station pump), set the cruise at about 65, and pulled in 31, 32, and 33 mpg. I was doing it to see how badly I needed a tune up now that 100,000 miles have finally rolled around. I will defer a little on this.
The low fuel mileage could be lots of things - tire pressure, an intermittent, hidden code, a less than clean throttle body, a faltering coil pack and/or plug wires, a worn out PCV valve, a loose vacuum hose, etc. All cheap enough fixes. Being diligent with easy stuff like oil changes, air filter changes, and fuel injector cleaner has kept mine running clean and economically. And always look under to hood to see what's askew. Next come the new plugs and plug wires for me.
There was also a batch - hopefully small - of Series III 3800 V6s that had some oil consumption issues, with a technical bulletin released, and I'd bet those didn't get the mileage that the tighter ones did.
