This part is pure media hype, IMO... It is right up there with TB spacers.
Or muffler bearings...
Or Blinker Fluid....
Seriously, there would be no appreciable loss of heat. I know that there are very strong opinions about engine oil coolers here on

. The overwhelming majority opinion is that they do nothing...
I respectfully disagree. They do work but, the installation
must be done properly or you create more problems than you solve.
There are two parts that must be installed in addition to the actual cooler itself. The first is a high volume oil pump and the second is a thermostat in the oil lines. It is imperative that the oil come up to the minimum operating temperature so it can shed the moisture and solvents it collects at shut down. If this is not done, the oil will turn acidic. Bad things happen to the bearings....
Example of a good thermostat:
http://www.jegs.com/i/Derale/259/25719/10002/-1?parentProductId=1335929#moreDetails
What you will see is that the T-Stat bypasses the cooler coil when the oil temperatures are below 180(F) with 90% of the oil bypassing the cooler. Why let any oil into the cooler? This is done to warm the cooler so as not to induce a thermal shock when the T-Stat operates.
I believe in coolers and would install one if I could only fine the space... In the past, I have used this exact T-Stat along with dual remote filter housings on all of the Hot Rods I have built. But, between the Flex-a-Lite transmission cooler and the PS cooler from an F350, there is no more room in front of the radiator.
The reason that you need a high volume oil pump is to promote a good flow rate through the entire system.
I would like to make a note here that my 1972 Mercedes 280 SEL 4.5 came with an engine oil cooler from the factory in Stuttgart... If they do nothing, why did Mercedes install one?