There's a few stats about the Fusion fuel currently that are a little...disappointing.

Considering:
- It's an endgame fuel, requiring considerable expense in terms of time and research.
- It uses a fluid ingredient, thus restricting it from guaranteed quality recipe setting.
- Uses moderately expensive ingredients.
- Stores only 2.5GJ out of 41.21GJ of energy sunk into it.

I'd propose the following stat changes.

• Fuel Value: 2.5GJ --> 6.156GJ

Nuclear Fuel (1.21GJ) as an example:
Made up of 1x U-235 (around 8GJ in a Uranium Fuel Cell) + 0.1GJ of Rocket fuel. 
This only uses 14.938% of total fuel energy in.

Perhaps the jump from Nuclear Fuel to Fusion Fuel (add 40GJ of Fusion cell) could be similar:
1 Fusion fuel, made up of 1x Fusion cell (40GJ) + 1 Fusion fuel (1.21GJ)
41.21 x 0.14938 = 6.156GJ

That is if you want to keep the same (in)efficiency of scale.

• Vehicle Acceleration: 300% --> 325%

From [anything] to Solid Fuel = +20% = 120%
From Solid Fuel to Rocket Fuel = +60% = 180%
From Rocket Fuel to Nuclear Fuel = +70% = 250%

Its a rapidly plateauing increase in acceleration, some napkin math would show...
From Nuclear Fuel to Fusion Fuel = +75% = 325%.
But considering its *Fusion Fuel*, perhaps even higher would be acceptable.

• Vehicle Top Speed. 120% --> 150%

[] --> SF = +5% = 105%
SF --> RF = +10% = 115%
RF --> NF = + 0% = 115% 

No real pattern, so this would have to be a slightly better reward than just 5%.

Ingredient-wise it seems pretty balanced, no complaints there.

This feedback makes sense! When I get a chance later today I think I'll implement most of this, though I'm unsure about the huge jump in top speed, since max quality fusion fuel would then be 225% top speed which seems maybe too wild compared to nuclear fuel's max quality 137.5%. Maybe having fusion's top speed at 130% or 140% at most?
Vehicle Acceleration I might make 350%, I'm a sucker for nice even numbers.
Fuel Value can definitely get a buff too, the only consideration I had when I chose the number was that I was a little upset that the stack size buff to rocket fuel meant nuclear fuel had a smaller fuel value per stack, I didn't even consider the energy value of the fusion cell when I set it, maybe 6 or 7.5GJ?
Thank you so much for the feedback!

6GJ is good. Vehicle acceleration 350% is good too.
Top speed 150% would be good, though. Yes, this means 225% legendary top speed, but for that you have to set up a sizeable Aquilo base just to make all this in legendary. Not easy, should be rewarded properly.

Part of me wonders if I should have made it a requirement to build the fusion fuel on Aquilo, but for myself I built it on Nauvis next to my nuclear fuel. Part of me wondered if I should've forced it to be only crafted on Aquilo, but I like the freedom of choosing where to make it.
Since it's built in the cryogenic plant you could get up to a 50% quality when crafting them, much better than what you can get from the centrifuge, making getting max quality much more feasible!
In any case, I recently added the ability to tweak the fuel, top speed, and acceleration, so you can change them to whatever you feel works best.

Oh yay! That means the "fusion fuel extreme" fork of the mod is now redundant? :D

Maybe? I didn't look at it beyond the surface but saw it had sulfuric acid as an ingredient so there might be other things it does!

Hi there! I loaded an existing save after changing the mod startup settings (changing top speed to 150%), but it didn't change in game – it still shows as 130% in the factoriopedia. I made sure that I used "load", not "sync and load". Could it be, that it simply didn't register in the factoriopedia or for the stats that are displayed on hover? Or is it actually unchanged? Looking at the mod startup settings while in the save, it's still at 150% so it didn't change back when loading or anything like that.

Do you need my save or can you reproduce that?

There's an additional startup value that needs to be changed in order for the custom values to be used, "Item stats and recipe mode", in order to use the custom startup values, it needs to be set to "Custom", if it's set to "Original" or "Slight buff" it'll use specific settings. Have you changed that setting as well?

Ah okay, that was the reason.
"Item stats and recipe mode" changes the recipe and the stats. Could it instead just change the recipe mode?

It's redundant to set defaults like that. After all, the defaults are already in each text field.