question: What's the difference between gasoline and diesel? Why is the other used over the other?
comment: **The Fuels** Both fuels are a mix of hydrocarbons, with diesel molecules having more carbon atoms on average. Gasoline behaves roughly like octane (8 carbon atoms) under combustion, hence the octane rating. Diesel behaves roughly like hexadecane (cetane, 16 carbon atoms), hence the cetane rating. The actual numbers of carbon atoms in gasoline molecules are around 4-12, and diesel molecules are around 12-20. **The Engines** Gasoline and diesel work well in engines that use the Otto cycle and Diesel cycle, respectively. The diesel engine reaches a higher pressure, and relies on auto-ignition of the fuel due to the high temperature associated with the increased compression. The higher pressure in a diesel cylinder means more force on the piston, and therefore more torque. Torque is useful for getting heavy loads moving (towing), so diesel is popular in trucks. The increased pressure also increases the efficiency of the engine. The drawbacks to diesel are: diesel engines are more expensive to build, it's harder to burn diesel cleanly, and diesel engines tend to run less smoothly.
passages: BULLET::::- Biodiesel is an easily synthesised, non-petroleum-based fuel (through transesterification) which can run directly in many diesel engines, while gasoline engines either need adaptation to run synthetic fuels or else use them as an additive to gasoline (e.g., ethanol added to gasohol).
   In North America, diesel engines are primarily used in large trucks, where the low-stress, high-efficiency cycle leads to much longer engine life and lower operational costs. These advantages also make the diesel engine ideal for use in the heavy-haul railroad and earthmoving environments.
  
  Section::::Applications.:Other internal combustion engines without spark plugs.
  
  Many model airplanes use very simple "glow" and "diesel" engines. Glow engines use glow plugs. "Diesel" model airplane engines have variable compression ratios. Both types depend on special fuels.
   Section::::Uses.:Military vehicles.
  
  Armored fighting vehicles use diesel because of its lower flammability risks and the engines' higher provision of torque and lower likelihood of stalling.
  
  Section::::Uses.:Cars.
   Section::::Origins.
  
  Diesel fuel originated from experiments conducted by German scientist and inventor Rudolf Diesel for his compression-ignition engine he invented in 1892. Diesel originally designed his engine to use coal dust as fuel, and experimented with other fuels including vegetable oils, such as peanut oil, which was used to power the engines which he exhibited at the 1900 Paris Exposition and the 1911 World's Fair in Paris.
  
  Section::::Types.
  
  Diesel fuel is produced from various sources, the most common being petroleum. Other sources include biomass, animal fat, biogas, natural gas, and coal liquefaction.
  
  Section::::Types.:Petroleum diesel.
   This category of diesel fuels involves converting the triglycerides in vegetable oil and animal fats into alkanes by refining and hydrogenation, such as H-Bio. The produced fuel has many properties that are similar to synthetic diesel, and are free from the many disadvantages of FAME.
  
  Section::::Types.:DME.
  
  Dimethyl ether, DME, is a synthetic, gaseous diesel fuel that results in clean combustion with very little soot and reduced NOx emissions.
  
  Section::::Storage.
   Section::::Uses.:Trucks.
  
  Diesel fuel is widely used in most types of transportation. Trucks and buses, which were often gasoline-powered in the 1920s through 1950s, are now almost exclusively diesel-powered. The gasoline-powered passenger automobile is the major exception; diesel cars are less numerous worldwide.
  
  Section::::Uses.:Railroad.
  
  Diesel displaced coal and fuel oil for steam-powered vehicles in the latter half of the 20th century, and is now used almost exclusively for the combustion engines of self-powered rail vehicles (locomotives and railcars).
  
  Section::::Uses.:Aircraft.
   Section::::Fuel and fluid characteristics.:Fuel types.
  
  In his 1893 work "Theory and Construction of a Rational Heat Motor", Rudolf Diesel considers using coal dust as fuel for the diesel engine. However, Diesel just "considered" using coal dust (as well as liquid fuels and gas); his actual engine was designed to operate on petroleum, which was soon replaced with regular petrol and kerosine for further testing purposes, as petroleum proved to be too viscous. In addition to kerosine and petrol, Diesel's engine could also operate on ligroin.
   Diesel
  
  Diesel may refer to:
  
  Section::::Science and technology.
  
  BULLET::::- Diesel fuel
  
  BULLET::::- Diesel engines and associated technologies:
  
  BULLET::::- Diesel cycle
  
  BULLET::::- Diesel–electric transmission
  
  BULLET::::- Diesel exhaust
  
  BULLET::::- Diesel exhaust fluid (DEF)
  
  BULLET::::- Diesel particulate filter (DPF)
  
  BULLET::::- And associated applications:
  
  BULLET::::- Diesel aircraft engine
  
  BULLET::::- Diesel generator
  
  BULLET::::- Diesel locomotive
  
  BULLET::::- Diesel motorcycle
  
  BULLET::::- Diesel multiple unit (DMU)
  
  BULLET::::- Dieselisation, term for the replacement of steam locomotives by diesel locomotives in the 1930s to 1960s.
  
  BULLET::::- 10093 Diesel, an asteroid named after Rudolf Diesel
  
  Section::::People.
  
  Section::::People.:By surname.
  
  BULLET::::- Nathanael Diesel (1692–1745), Danish composer, violinist and lutenist
   Before diesel engine fuel was standardised, fuels such as petrol, kerosine, gas oil, vegetable oil and mineral oil, as well as mixtures of these fuels, were used. Typical fuels specifically intended to be used for diesel engines were petroleum distillates and coal-tar distillates such as the following; these fuels have specific lower heating values of:
  
  BULLET::::- Diesel oil: 10,200 kcal·kg (42.7 MJ·kg) up to 10,250 kcal·kg (42.9 MJ·kg)
  
  BULLET::::- Heating oil: 10,000 kcal·kg (41.8 MJ·kg) up to 10,200 kcal·kg (42.7 MJ·kg)
  
  BULLET::::- Coal-tar creosote: 9,150 kcal·kg (38.3 MJ·kg) up to 9,250 kcal·kg (38.7 MJ·kg)
  
  BULLET::::- Kerosine: up to 10,400 kcal·kg (43.5 MJ·kg)
  
  "Source:"
   The most common type of diesel fuel is a specific fractional distillate of petroleum fuel oil, but alternatives that are not derived from petroleum, such as biodiesel, biomass to liquid (BTL) or gas to liquid (GTL) diesel, are increasingly being developed and adopted. To distinguish these types, petroleum-derived diesel is increasingly called "petrodiesel". Ultra-low-sulfur diesel (ULSD) is a standard for defining diesel fuel with substantially lowered sulfur contents. As of 2016, almost all of the petroleum-based diesel fuel available in the UK, mainland Europe, and North America is of a ULSD type. In the UK, diesel fuel for on-road use is commonly abbreviated "DERV", standing for "diesel-engined road vehicle", which carries a tax premium over equivalent fuel for non-road use. In Australia, diesel fuel is also known as "distillate", and in Indonesia, it is known as "Solar", a trademarked name by the local oil company Pertamina.
   Section::::Uses.:Tractors and heavy equipment.
  
  Today's tractors and heavy equipment are mostly diesel-powered. Among tractors, only the smaller classes may also offer gasoline engines. The dieselization of tractors and heavy equipment began in Germany before World War II but was unusual in the United States until after that war. During the 1950s and 1960s, it progressed in the US as well.
   Section::::Multiple fuel source.:Dual Fuel.
  
  Dual fuel vehicle is referred as the vehicle using two types of fuel in the same time (can be gas + liquid, gas + gas, liquid + liquid) with different fuel tank.
  
  Diesel-CNG Dual Fuel is a system using two type of fuel which are diesel and Compressed Natural Gas (CNG) at the same time. It is because of CNG need a source of ignition for combustion in diesel engine.
  
  Section::::Multiple fuel source.:Flexible fuel.
   BULLET::::- CX-3
  
  BULLET::::- CX-5
  
  BULLET::::- CX-8
  
  BULLET::::- BT-50
  
  Section::::Mercedes-Benz.
  
  Former
  
  BULLET::::- W110
  
  BULLET::::- W120
  
  BULLET::::- W123
  
  BULLET::::- W124
  
  BULLET::::- W201
  
  BULLET::::- W136
  
  BULLET::::- W126
  
  BULLET::::- CLC-Class
  
  BULLET::::- CLK-Class
  
  BULLET::::- R-Class
  
  BULLET::::- Vario
  
  Current
  
  BULLET::::- A-Class
  
  BULLET::::- B-Class
  
  BULLET::::- C-Class
  
  BULLET::::- E-Class
  
  BULLET::::- S-Class
  
  BULLET::::- CLA-Class
  
  BULLET::::- CLS-Class
  
  BULLET::::- GLA-Class
  
  BULLET::::- GLC-Class
  
  BULLET::::- GLE-Class
  
  BULLET::::- GLS-Class
  
  BULLET::::- G-Class
  
  BULLET::::- SLK-Class
  
  BULLET::::- X-Class
  
  BULLET::::- Citan
  
  BULLET::::- Vito
  
  BULLET::::- Sprinter
  
  Section::::Mercury.
  
  BULLET::::- Lynx
  
  BULLET::::- Topaz
  
  Section::::Mini.
  
  Former
  
  BULLET::::- Coupé/Roadster
  
  BULLET::::- Paceman
  
  Current
  
  BULLET::::- Hatch
  
  BULLET::::- Clubman
  
  BULLET::::- Countryman
  
  Section::::Mitsubishi.
  
  BULLET::::- Lancer
  
  BULLET::::- L200
  
  BULLET::::- Libero
  
  BULLET::::- Pajero
  
  BULLET::::- Delica
  
  BULLET::::- adventure
  
  Section::::Nissan.
   Unlike gasoline and liquefied petroleum gas engines, diesel engines do not use high-voltage spark ignition (spark plugs). An engine running on diesel compresses the air inside the cylinder to high pressures and temperatures (compression ratios from 14:1 to 18:1 are common in current diesel engines); the engine generally injects the diesel fuel directly into the cylinder, starting a few degrees before top dead center (TDC) and continuing during the combustion event. The high temperatures inside the cylinder cause the diesel fuel to react with the oxygen in the mix (burn or oxidize), heating and expanding the burning mixture to convert the thermal/pressure difference into mechanical work, i.e., to move the piston. Engines have glow plugs and grid heaters to help start the engine by preheating the cylinders to a minimum operating temperature. Diesel engines are lean burn engines, burning the fuel in more air than is needed for the chemical reaction. They thus use less fuel than rich burn spark ignition engines which use a stoichiometric air-fuel ratio (just enough air to react with the fuel). As Professor Harvey of the University of Toronto notes, "due to the absence of throttling [constant amount of air admitted, per unit fuel, with no user-determined variation], and the high compression ratio and lean fuel mixture, diesel engines are substantially more efficient than spark-ignited engines", generally; Harvey cites the side-by-side comparisons of Schipper et al. and the estimates of 20% lower fuel use and (given differences in energy content between fuel types) 15% lower energy use. Gas turbine and some other types of internal combustion engines, and external combustion engine, both can also be designed to take diesel fuel.
   Section::::Advertising.
   So-called dual-fuel diesel engines or gas diesel engines burn two different types of fuel "simultaneously", for instance, a gaseous fuel and diesel engine fuel. The diesel engine fuel auto-ignites due to compression ignition, and then ignites the gaseous fuel. Such engines do not require any type of spark ignition and operate similar to regular diesel engines.
  
  Section::::Diesel engine particularities.
  
  Section::::Diesel engine particularities.:Torque and power.
   Petroleum diesel, also called "petrodiesel", or fossil diesel is the most common type of diesel fuel. It is produced from the fractional distillation of crude oil between and at atmospheric pressure, resulting in a mixture of carbon chains that typically contain between 9 and 25 carbon atoms per molecule.
  
  Section::::Types.:Synthetic diesel.
  
  Synthetic diesel can be produced from any carbonaceous material, including biomass, biogas, natural gas, coal and many others. The raw material is gasified into synthesis gas, which after purification is converted by the Fischer–Tropsch process to a synthetic diesel.
   Gasoline engines that are much smaller than the typical automotive engine are usually carbureted for economic and engineering reasons. Dieseling can occur in such engines. These engines include those installed in small generators, mopeds, scooters, small motorcycles, all-terrain vehicles, and most lawn and garden power tools.
  
  Section::::Potential causes.
  
  Dieseling can occur for several reasons:
   Presently, fuels used include:
  
  BULLET::::- Petroleum:
  
  BULLET::::- Petroleum spirit (North American term: gasoline, British term: petrol)
  
  BULLET::::- Petroleum diesel.
  
  BULLET::::- Autogas (liquified petroleum gas).
  
  BULLET::::- Compressed natural gas.
  
  BULLET::::- Jet fuel (aviation fuel)
  
  BULLET::::- Residual fuel
  
  BULLET::::- Coal:
  
  BULLET::::- Gasoline can be made from carbon (coal) using the Fischer-Tropsch process
  
  BULLET::::- Diesel fuel can be made from carbon using the Fischer-Tropsch process
  
  BULLET::::- Biofuels and vegetable oils:
  
  BULLET::::- Peanut oil and other vegetable oils.
  
  BULLET::::- Woodgas, from an onboard wood gasifier using solid wood as a fuel
  
  BULLET::::- Biofuels:
  
  BULLET::::- Biobutanol (replaces gasoline).
  
  BULLET::::- Biodiesel (replaces petrodiesel).
   Section::::Applications.:Railroad rolling stock.
   Section::::Fuel and fluid characteristics.:Gelling.
   List of diesel automobiles
  
  The following is a list of automobiles (including pickup trucks, SUVs, and vans) made with diesel engines.
  
  Section::::Alfa Romeo.
  
  Former
  
  BULLET::::- 145
  
  BULLET::::- 146
  
  BULLET::::- 147
  
  BULLET::::- 155
  
  BULLET::::- 156
  
  BULLET::::- 159
  
  BULLET::::- 164
  
  BULLET::::- 166
  
  BULLET::::- 33
  
  BULLET::::- 75
  
  BULLET::::- 90
  
  BULLET::::- Alfa 6
  
  BULLET::::- Alfetta
  
  BULLET::::- Brera
  
  BULLET::::- GT
  
  Current
  
  BULLET::::- Guilia
  
  BULLET::::- Stelvio
  
  BULLET::::- MiTo
  
  BULLET::::- Giulietta
  
  Section::::Audi.
  
  Former
  
  BULLET::::- 80
  
  BULLET::::- 90
  
  BULLET::::- 100
  
  BULLET::::- 4000
  
  BULLET::::- 5000
  
  BULLET::::- Allroad
  
  BULLET::::- A2
  
  Current
  
  BULLET::::- A1
  
  BULLET::::- A3
  
  BULLET::::- A4
  
  BULLET::::- A5
  
  BULLET::::- A6
  
  BULLET::::- A7
  
  BULLET::::- A8
  
  BULLET::::- Q2
  
  BULLET::::- Q3
   Section::::Diesel conversions.
  
  Diesel engine is compression ignition engine and does not have spark plug. To operate a diesel engine with an alternate combustible fuel source such as Natural gas, Dual-Fuel system used. Natural gas as the main fuel while diesel fuel is used for the ignition of the gas/air mixture inside the cylinder (a portion of diesel is injected at the end of the compression stroke, thereby maintaining the original diesel operation principle)
   BULLET::::- Diffusion flame: At combustion, oxygen first has to defuse into the flame, rather than having oxygen and fuel already mixed before combustion, which would result in a premixed flame.
  
  BULLET::::- Fuel with high ignition performance: As diesel engines solely rely on compression ignition, fuel with high ignition performance (cetane rating) is ideal for proper engine operation, fuel with a good knocking resistance (octane rating), e.g. petrol, is suboptimal for diesel engines.
  
  Section::::Operating principle.:Cycle of the diesel engine.
   BULLET::::- Common rail mechanical injection, where fuel is at high pressure in a common rail and controlled by mechanical means.
  
  BULLET::::- Common rail electronic injection, where fuel is at high pressure in a common rail and controlled electronically.
  
  Section::::Fuel injection.:Torque controlling.
  