I've got two 13" MBP's (Mid 2012) here at home and I've been observing the temperatures for the last half hour. One is 5-8 C cooler than the other one. I'm using smcfancontrol on both of them and have the fans set at 2400 on both as well. The main difference between the two machines is that the warmer machine has an SSD drive, but everything else is the same. Both are running on batteries, both are running the same programs (mail, chrome, activity monitor). The warmer machine will idle at 48-50 C while the cooler machine will idle at 40-42 C. Seems a bit of a difference, isnt it?