The manual obviously says to use 75w140 synthetic in the front and rear for towing. After looking through the stores there is a huge price difference between that weight and 85w140(non-synthetic right?). Usually I just go with the recommended and be done with it but in this case it is $6.99 vs $12(for 75w140 syn supertech walmart crap) or higher, $20+ for mobile1 and royal purple per qt.

Seems to me that the heaver weight non synthetic stuff might do just fine but Im not so sure. Im all for being thrifty but a trashed diff will kill the thriftiness of the cheaper oil. FYI the parts stores keep recommending 85w as its summer.
I am going to change the fluid ether way because they need to be done(way over 30k miles) and Ill be moving to Oregon soon and towing a trailer but Im in extreme penny pinching mode as Im jobless for the moment.
Its and 05 Renegade 3.7 with trashlok. Yes I have the friction modifier from the dealer already.

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So it goes.

85w-140 will be much better then full syn gear oil,run cooler and the bearings will last longer.All I run is 85w-140.

Lucas Oil sells an 85/140 full synthetic for about $9.00 and you don't need any posi- additives.