I couldn't find the relevant information in the list of changes, but as far as I remember, the fuel values ​​were lower before. (Did it increase by x10, did I mix something up?) As far as I remember;

Petroleum Gas: While it had a fuel value of 1.2 MW, it is now 12 MW (10 times increased)

This seems excessive to me.

1-) How can I edit it?

2-) Is my mind deceiving me about this change, or is it a x10 increase compared to the old versions

Yes, i've changed the values from 1/10th to 1 and they now match solid-fuel values.

The change was made in 1.1.2 in which i set the new values.
You can change this in functions.lua, lines 8 to 11. These values use solid-fuel as reference and to change the reference just put in another item with fuel_value. You can also set in your own magic number at line 35.

First of all, thank you for both the mod and the explanations and answers.

But with the change, it is not compatible with solid fuel, it is incompatible. In other words, it was compatible in the old version.

Because

20 Heavy Oil= 1 Solid Fuel => 12 Mj
10 Light Oil= 1 Solid Fuel=> 12 Mj
20 Petroleum Gas= 1 Solid Fuel=> 12 Mj

In this case, if the correct ratio / compatibility is sought,
1 Light Oil should be 12/10=1.2 Mj.
Because this is the best recipe ratio.

Long story short; you are equating 1 unit of fuel to 1 solid fuel; whereas in recipes this amount is (20-10-20).

https://wiki.factorio.com/Solid_fuel

Yes, you're right. There is a relation between solid and liquid fuel values.
Since you can not burn solid fuel in these machines it really doesn't matter. What matters is the fuel value to energy conversion ratio if you want to compare steam engines/turbines and the mods generators. A steam engine produces 900 KW or 0.9 MW which in comparsion with a gas generator which generats 2.4 MW. Using the 2.4MW as a base we see that a steam engine only produces 37.5% as much power. Now we must calculate the needed energy to convert light oil into solid fuel, see how long a block of fuel lasts (but for 2 steam engines per burner) and keep in mind, that a gas engine only uses 1/10 fluid per second where a steam engine uses 1 steam ... and so on etc pp

It gets complicated for no benefit. At the end of the day, all you do is to burn your excess fluids.
Even on Fulgora it is just a fallback option if your accumulators ran dry.

But change it as you please.