Hi I am new here I have been looking around quite a bit but still do not understand what I am looking for in a oil or gear oil. I have a 2003 Dodge 3500 4x4 with the Cummins diesel & 6 speed tranny. I want to change the front & rear differential oil. I tow a 11,000 pound boat in the summer almost every weekend. They call for a 75w-140 synthetic the two I have been considering is the Mobil 1 & the Amsoil severe gear. Which would be the better or is there something else out there better?
Thanks Charlie