Engine efficiency improvement through higher temp thermostat?

[Cobb]

Right on. Most automatics run the cooler through the coolant at the bottom of the radiator. Others use an engine oil cooler like at the oil filter.

I fooled with a radiator vs grill block to hold mo heat in my engine and too notice the timing retard. T stat opens full at 180, 190 timing starts to retard. 200 low speed fan comes on 220 high speed.

What I ended up doing was blocking the outer grill and running water wetter to keep the engine in the 180 zone to keep timing and block the outer edge for more aero.

[gumby79]

Forgive my old no computer truck '91 Dodge Cummings
I was told by previous owner that the thermostat had ben reduced to a 175° for better FE. (See fancluch )
So iwas thinking of going back to stock185°or higher, however , last week. I was stuck in. 20-30M.p.h. traffic on tehacapi pass westbound between backer and tehacapi 105°ambient ac on.FE was down almost 5mpg because the mechanical thermal clutch was running the hole time. Ok some specs
Normal. Northwest. 40-75°f
Warming to 175° pop gos the thermostat drops th 165° and stays +-5° fan no engagement. Long steep grades ive seen as high as185°f empty

Hot weather Las Vegas 100-115°f
Warming to 175° pop downto 165°-(192 with ac) it will cycle with road speed. And fan cycle
Temp read with digital gauge
Fan cycle
Locked in at181°released at172°f

So conclusion. Increase thermostat to 185°will KILL my FE. Because the fan come on 5°befor the thermostat pops
Fan in lockup pulls about 15hp

If i spend $4-500on electronic fans. Plus controller. (To solve macanical fan hp draw) how hot will my Cummings be happy ?210°with 250°peek? (Will require a waterless. Coolant!!!) what kind of FE %increase canbe experienced? $500÷mpg gained =yearsto payoff?
as for trans I'll probably have ro take out the 3rd stock trans cooler. As it is coolant/to liquid (simaler to the one in the radiator)but on the frame under the exost manifold

[oil pan 4]

There should be an adjustment screw to turn the engagement temperature up or down on the fan clutch.
Try that first, get the fan clutch to where the thermostat can open most if not all the way then have the fan come on once passive air flow isn't enough to cool it down.

We had a guy that would take stock duramax fan clutches, turn the engagement adjustment screw down 5 or 10 degrees, resell them for $100 more as up "grade fan clutches" for 6.2L and 6.5L diesel engines.

[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.