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Depending on the type, engines require different types of fuel or materials to run. What they all have in common however is that they need a redstone signal (e.g. from a Lever) to work.
Any of these machines can be broken with a wooden pick or better.
 Buildcraft 3 Engines
One common property of the vanilla Buildcraft engines is that they will explode if they get too hot. As an engine heats up, its color will change from blue to green to yellow to red, before exploding. An engine that is solid (not blinking) red is about to explode and should be shut off immediately.
The Redstone Engine is the most basic engine, only needing to be turned on using a redstone signal to run. It has a very low power output (1MJ/s or 0.05MJ/t), and takes roughly 1.5 Minecraft days to warm up and reach this output. Most machines won't accept power from a Redstone Engine, except Thermal Expansion and Railcraft machines, and certain Buildcraft machines (such as the Pump). They are most commonly used to power Wooden Transport Pipes to remove items from a chest.
The Steam/Stirling Engine is an upgrade of the Redstone Engine. It is significantly more powerful, producing 1 MJ/t, but uses fuel such as coal. It will eventually explode if it is producing more power than is being used.
Combustion Engines are the most expensive type of Buildcraft engine, but are also the most powerful, capable of producing up to 6MJ/t. They require fuel such as Lava, Fuel or Oil to run, and if not looked after correctly are prone to explosion. It is necessary to keep them cool to avoid an explosion.
The Biogas Engine can be fueled by Water, Milk, Honey, Seed Oil or Biomass. It also requires Lava to start up, but will never overheat. Depending on the fuel, Biogas Engines produce between 1 MJ/t to 5 MJ/t.
The Peat-fired Engine requires Peat or Bituminous Peat to run and will produce Ash during the process. It will output 1 MJ/t to 2 MJ/t depending on the fuel. It will stop working once there's too much ash stored.
 Thermal Expansion Engines
These engines have three properties which are common to Thermal Expansion machines but are absent in other engines:
- When connected to Redstone Energy Conduits, the conduit must be set to accept energy from the engine (orange arrow points away from engine). Other engines currently ignore this.
- Their response to a redstone signal is configurable. By default, they run except when they are receiving a redstone signal.
- They can overheat, but don't explode - if their internal energy buffer fills, they "break" and require being whacked by a Buildcraft Wrench or Crescent Hammer before they will run again.
The Steam Engine requires solid fuels (such as Coal) as well as Water. It outputs between 0.2 MJ/t and 2 MJ/t, and will overheat and stop working if it has nothing to power, this can be remedied by simply clicking it with a Buildcraft Wrench or a Crescent Hammer.
The Magmatic Engine requires lava to run. It outputs between 0.4 MJ/t and 4 MJ/t, and will overheat and stop working if it has nothing to power, this can be remedied by simply clicking it with a Buildcraft Wrench or a Crescent Hammer.
 Recipe(New Recipe)
Railcraft engines run on steam - either produced within the engine or externally. The engine color will change from blue to green to yellow to orange to red as its internal buffer fills up - if the engine overheats it will "break" - whack it with a wrench in order to restart it.
The Hobbyist's Steam Engine requires solid fuels (such as Coal) as well as Water. Once it reaches 100 C, it will produce steam, reaching a maximum generation rate of 1.6 MJ/t. It can also instead be fed steam directly from a Steam Boiler, generating 2 MJ/t. Beware: If it runs out of water, it will overheat. Adding water to a hot, dry engine will result in an explosion.
The Commercial Steam Engine generates twice as much power as the Hobbyist's Steam Engine, generating 4 MJ/t. However, it does not have an internal boiler, thus you must supply steam from an external source (Steam Boiler).
The Industrial Steam Engine generates twice as much power as the Commercial Steam Engine, generating 8 MJ/t, and consumes steam twice as quickly.
The Blulectric Engine produces MJ from Blutricity. The engine can consume a large amount of blulectric power, producing up to 32 MJ/t, but it will automatically scale back if it detects that the connected machine cannot use all this power. Unlike other engines, this engine must be rotated with a Screwdriver.