Fuel is the result of refining Oil in an Oil Refinery. It can then be used in Combustion Engines or to fuel Jetpacks with a Jetpack Fueller. Fuel generates about 7.5 times more energy than a bucket of Oil when used in a Combustion Engine.
Fuel is the highest tier of fuel when used in a combustion engine. It produces far more than a bucket of both oil and lava.
Fuel has no EMC value, because there is no item with any EMC value to compare it with.