Mobil 1 75/140 syn gear lube

[cowboywildbill]

Have 3800 miles on truck and I just purchased 4 quarts to change my diff. I went with the 75/140 because we tow very heavy. It was $14.99 per quart as opposed to Mobil 1 75/90 that cost half of that. Someone told me they blend half 75/90 and 75/140 ?
I have not tried that. Any suggestons ? I wouldn't think that the mpg would be much different between the two. Thanks

[Inspector]

I did about 1k on my new truck in 03 and dropped the grape juice out and put in Amsoil 75/140. I also tow heavy. I think that for us guys that do tow heavy that weight combination is a good idea. The rear diff runs cool as a cucumber.
Denny

[murphyslaw]

I put 75/90 in our tow trucks(commercial towing)