[MkVer]

A rule of thumb for transmission temps; every 20 degrees over rated temperature cuts the life of your transmission fluid by 20,000 miles.

My truck transmission runs about 15 degrees below the engine temp with an independent cooler that could be relocated if I wanted to bump my coolant temps up. My car cools the transmission with a oil to water(coolant) heat exchange so the temps are almost identical. I'd check your set up to see what effect your going to have on your transmission temps. An FE/environmental gain might be lost with the increased cost of transmission fluid changes.