Why cool your fuel?

[Lonesome7.3]

I noticed lately that some people are cooling their diesel fuel. I know in a gasser that is a good thing and helps performance. But I was under the impression it is better to heat your diesel fuel. Was I taught wrong? What are the benefits of installing a fuel cooler on your diesel powered vehicle?

 

[Ironman03R]

Coolers are for the comonrail trucks, the high pressures create more heat so the fuel needs to be cooled back to normal temps.
The guys that are heating there fuel are usually running alternative fuel and need the the temp of the fuel to be higher for a more complete burn and/or to thin it out.

 

[Lonesome7.3]

I thought that was part of it. I also thought the heating of the deisel and thinning it was a good thing as well. But it is starting to look at though I had it backwards.