Some information from Ford for those of you fighting with your MT82 in cooler weather.
Some 2011-2012 Mustang vehicles equipped with a MT82 6-speed manual transmission may exhibit increased shift efforts in cold ambient temperatures. This is usually most noticeable in 1st and 2nd gears but may also be noticed in 3rd through 6th gears. The increased shift effort may be the result of the increased viscosity of the transmission fluid in cold weather.
Follow the Service Procedure to correct the condition.
Replace the MotorcraftFull Synthetic Manual Transmission Fluid with 2.6L (2.7 qt) of Motorcraft Dual Clutch Transmission Fluid. Refer to Workshop Manual, Section 308-03A for the transmission fluid draining and filling procedure.
This fluid is suitable for use in all ambient temperatures and seasons, and the Scheduled Maintenance guidelines in the Owner Guide can continue to be followed.
The use of friction modifiers or other fluid additives is not recommended since although they may provide some immediate improvement in cold shift effort, they are likely to result in long term degradation of the synchronizers.
Download the pdf here: Ford Mustang TSB -11-03-18