2007 Mazda3 2.3 liter might have problems

Hi Eric. One thing you need to understand is that what the computer tells you is a snap shot in time based on the info it's pulling from the engine and assumed information. You can't really judge the mileage until you actual do the math on your fuel consumption. The rated mpg is based on steady consumption and as the saying goes your results will vary based on any number of factors including some that have nothing to do with the vehicle like your driving style, quality of gas, elevation and other environmental concerns. And only you know where your average driving falls between "city" and "highway". You aren't going to land on those mileage ratings exactly of course but if you aren't even the ball park you have a right to have the car checked. As for the squeaking, anything is possible but I'd have a hard time buying that when swallowing a new car payment. If that's the case a little WD-40 would relieve the squeak at least temporarily and they'd have to show me that that is indeed the case. Try another dealership on that one. Good luck!