What is AMD FUEL service?

As it turned out, it's responsible for the additional Performance and Power options in Catalyst Control Center:

Here's that you get without it:

and with it enabled:

It has to do with Catalyst Control Centre. Here some info.

While we are not 100% of the role of this service, from the tests we have run this service seems to only be used by Windows if you have set up various graphics profiles within the AMD/ATI Catalyst software to cater for various graphics configurations (this feature will typically be used mainly by gamers or users working in the graphics industry such as movie or video editing, etc...). Our guess at the time of writing, 12-May-2012, is that at boot-up it sets up your graphics card for the profile you have chosen, and it helps in the switching to other profiles if you should choose to do that.

So keeping it on is up to you. There haven't been problems reported by disabling it.

NOOOO!
Don't disable the AMD Fuel service!
If you have an AMD CPU, this is what lets dynamic clock rates happen!

Without it, even if Cool 'n Quiet is enabled in BIOS, your power management settings will not include an item to set a minimum CPU speed. You will always be running at full throttle and full heat! Even AMD Overdrive will not be able to make the clock run slower than the max.

Note that this service will kill the "turbo boost" feature, which allows your CPU to overclock to a BIOS-selected speed automatically when it's executing only one thread. But I have a 9590 with 4.7 GHz nominal and 5.0 GHz turbo and it runs hot as a M.F.

I would much rather have that chip run cool at 20% speed nearly all the time and jump to 4.7 when needed, rather than run at 4.7 all the time at 60ºC, even though it would jump to 5.0 GHz when needed.

MORE ABOUT THAT EXTREMELY HOT PROCESSOR:
It is impossible to run all 8 cores of a 9590 at 100% utilization for more than a few seconds. It will go into emergency thermal shutdown every time. I have a liquid-cooling system I designed myself with FIVE 120mm fans (all on the same side of the radiators, which means I could run 10 fans in push-pull). I use half-inch hose and a super-power pump, and it STILL overheats with 8 cores at 100%, even with the clock set low at 4.0 GHz.

I even got a kilowatt power supply and added a 420-watt Peltier TEC (which is an interesting story all by itself). But the thermal bottleneck seems to be in the chip/waterblock interface. It's just not possible to push any more heat through a 40 mm² of copper without the hot side getting too hot.

I got a 50x100 mm plate so I can split the hose and add a second waterblock, but I still have to buy the waterblock and fittings. What's holding me back (besides the cost) is that I'd have to make a custom bracket to hold the whole thing down against the CPU. I just haven't gotten around to drilling holes in aluminum with my Dremmer yet, even though I got the diamond-studded aluminum-cutting bit for that purpose.

Instead, I disabled 4 of my 8 cores. If you have a 9590, DO IT. Now I can run the other 4 at full-throttle.