It is my attempt to balance the efficiency of fluid transportation using fluid wagons and/or cargo wagons with barrels.
As stated here: (https://forums.factorio.com/viewtopic.php?f=16&t=46845&start=20#p274057)
I have a strong feeling that the vanilla fluid wagon is too OP. Graphically, it just doesn't match its insane capacity, which is x3 of a single storage tank. It also makes long fluid train to be rare, since 1 or 2 fluid wagons are already enough.
Therefore, I nerfed it. But that thread also showed that it is necessary to also nerf barrel.

Here are the changes introduced by this mod:
Fluid wagon:
* The capacity of fluid wagon is reduced from 75k to 30k (10k for each tank). So now you need longer trains to transport fluid.
* Due to the above change, the weight of each fluid wagon is reduced from 3000 to 1000, which becomes the same as a cargo wagon.
* Only 1 storage tank is needed to make a fluid wagon instead of 3. This reduces the total crafting time and raw materials needed from 1.4ks and 243 iron ore to 915s and 153 iron ore respectively. A cargo wagon takes 845s and 140 iron ores.
* Crafting time is reduced from 1.5s to 0.5s, which becomes the same as cargo wagon.

Barrel:
* The capacity of each barrel is reduced from 250 to 100.
* Stack size is reduced from 10 to 5. As the result, each cargo wagon can now only hold 100x5x40 = 20k fluid.
(It is intentional to make the max fluid capacity of cargo wagon to be smaller than that of a fluid wagon.)

For bug reports and general discussions, please go to our forum thread.