I am having a problem with the hydraulics not working at all on my 7245 when the outside tempatures get below freezing. It seems that the colder the temps the longer it takes for the hydraulics to start working. Sometimes I have to let the machine idle for an hour before the hydraulics start to work. I installed a new internal hydraulic pump 2 years ago and the first winter it worked great, then last winter I started having these issues. I replaced the 80/90W hydraulic oil when I replaced the pump. Should I be using a lighter oil in the winter? I live in Maine and I operate the tractor sometimes as cold as 0 degrees farenhite.