Primitive:

Furnace Cart:

Basic engine running on the convection of heat and motion (read: magical handwaves) to operate the cart. Difficult to automate, but can handle early game shunting

Accepts:

• Coal
• Charcoal

Steam:

Requirements:

• Water
• Fuel

Low-Pressure Steam Locomotive:

Basic engine running on the heating of water to create steam which creates the power to operate the engine. Reliable design good for shunting and medium-range builds.

High-Pressure Steam Locomotive:

A more complicated engine running on the heating of water to create steam, which is further heated in a superheater to make superheated steam. Is more efficient, but requires a massive amount of fuel to start up and is dangerous if there is a failure. Good for long-range builds.

Upgrade:

Oil Burning:

Grants ability to use certain types of liquid fuel instead of solid fuels by converting the firebox. Cannot handle gasses or upward flowing liquids however as they would simply exit through the Chimney.

Fuel Types:

• Anything in a furnace
• w/ Oil Burning upgrade: Lava, Creosote, Liquefacted Coal, anything that isn't a literal gas (marked as such in the fluid dictionary) or floats upward (marked as such in the fluid dictionary)

Electric

Requirements:

• Electric Track
• Railcraft Charge capability

Electric Locomotive:

Engine that draws on outside power to operate. Highly efficient and reliable, but requires additional infrastructure in order to work well.

Fuel Types:

• Railcraft Charge

Diesel

Requirements:

• Chem Lab

Diesel-Electric:

Engine that contains an onboard alternator to generate power for the engine from hydrocarbons. More efficient than an oil burner and reliable, but is expensive to operate due to the need to use processed hydrocarbons rather than any old type of fuel.

Fuel Types:

• Diesel
• Ethanol
• Biodiesel
• other processed fuels

Magic:

Essentia:

Engine that uses literal magic to power itself from Thaumcraft essentia.

Fuel Types:

• Thaumcraft Essentia

My thoughts.

Would the oil burning upgrade be for Primitive and Steam or only steam?
Could the Magic locomotive also take Botania mana? I believe there's already a mana cart.
Perhaps an upgrade for the Diesel locomotive could be a Hybrid upgrade, where it also charges/discharges from an energy cart (charges when idling and discharges when more power is needed)

anything that isn't a literal gas (marked as such in the fluid dictionary) or floats upward (marked as such in the fluid dictionary)

This needs some obvious changes considering 'water' fits the bill, but a whitelist will probably do.

Probably a separate mana cart.

I like the tought of a magical train...

Besides that this could be a very good idea 👍

ww should have a Jet Fuel train that is made out of steel so that conspiracy theorists of the 9/11 incident will go : "jet fuel can't melt steel beams"
(NOTE : this was actually sarcasm i am not actually thinking this would be implemented)

Twist: Jet Fuel train fueled by enderio rocket fuel

I'd suggest a train fueled by vanilla rocket