Top 10 different car fuel types

Cars & Light Trucks, Crude Oil, Oil, Gas & Coal, Personal Energy, Personal transport, Transportation / By

We often hear of diesel, gasoline, hybrid, and electric vehicles. However, there are actually quite a few different ways of fueling a car. Some of them can be interchanged with your existing car, some need a small modification, while others would require a full overhaul. Below we list the top 10 ways of fueling a car. In the US, anything except petrol and diesel is considered an alternative fuel. In China, New Energy Vehicles include Hybrid, natural gas, and electric vehicles. The 10 different fuel types talked about in this article are:

  1. Gasoline / petrol
  2. Diesel fuel
  3. Hybrid (non-plug in)
  4. Plug-in Hybrid
  5. Electric
  6. CNG / Propane
  7. LPG / Autogas
  8. Hydrogen ICE
  9. Hydrogen fuel cell
  10. Solar
  11. Other methods
PON numbers at a US gas station

Gasoline / petrol

Gas or petrol is the most common fuel type. Internal Combustion Engines (ICEs) with diesel fuel rely on spark plugs to ignite the fuel-air mixture after it is compressed. With around 45% of every barrel of oil being refined into gasoline, the demand for this fuel is the largest of all car propulsion types. However, even within this category, there are different qualities and mixtures.

Often ethanol is added to the gasoline fuel mixture, which can be mandated based on different national regulations across the globe. Ethanol is often derived from corn or other biomass. The addon doesn’t’ normally impact the car’s power, however, may lead to slightly higher fuel consumption. It was previously believed that corn-based ethanol could be cost competitive with conventional gasoline, however, this is now seen as largely false.

Iso-Octane: the standard 100-point on the octane rating scale

Octane rating describes the ability of the fuel to resist ignition while being compressed. The iso-octane isomer of (C8H18) is the 100 point, with the n-heptane isomer of (C7H16) being the 0 point. In Europe and most places in the world, the Research Octane Number (RON) is used, which compares these two molecules burning at 600rpm in lab conditions to the fuel being tested in a test engine, with no pre-heating of the fuel and constant ignition timing. Another fuel rating, the Motor Octane Number (MON) uses the same lab conditions, however, runs the engine at 900rpm with pre-heating the fuel mixture to 150C and using variable ignition timing.

The MON stresses the engine more and gives a lower number than the RON. In the US, Canada, Brazil, and some other countries, the average of the MON and RON is posted at fuel stations. This number can be called the Anti-Knock Index (AKI), the Posted Octane Number, or Pump Octane Number (PON). The difference between the PON posted in North America and the RON posted in Europe leads to some confusion about the quality of gasoline in North America. A PON of 93 in the US can be equivalent to a RON of 98 in Germany if the MON is 87 ((87+98)/2=92.5). A higher octane rating is desirable in performance engines since it delays ignition, allowing for more compression in the engine.

Diesel

Diesel fuel is the fuel of choice for most trucks, semis, and lorries, and up until 2017 was the fuel of choice for European customers. Most diesel fuel comes from a specific fractional distillation of crude oil, with on average 24% of crude becoming diesel. Recently diesel fuel has also come from other sources like biodiesel, biomass to liquid (BTL) or gas to liquid (GTL). Because diesel fuel is denser than gasoline, diesel vehicles often have much longer ranges than gasoline cars, on the order of 450 miles (750 km).

Diesel cars operate by compressing the air, then injecting fuel right before the top-dead-centre rotation of the piston, allowing the fuel-air mixture to increase in pressure and temperature to the point of ignition. In cold climates, glow plugs, block heaters, and grid heaters can be used to ensure that the engine and fuel are at a high enough temperature to start ignition.

Many modern cars burn on ultra-low sulphur diesel (ULSD) which removes most of the harmful sulphur from the fuel is now the most common type of diesel fuel in Europe and most other countries. ULSD decreases wear on engines and exhaust components and decrease soot emissions since particulate is often removed as well.

Diesel vehicles have fallen out of favor in Europe after the dieselgate scandal showed that European car manufacturers were cheating on emissions tests. As a fallout from this scandal, many of these manufacturers have now pivoted to promote hybrid and electric vehicles as alternative fuel vehicles.

Hybrid

Hybrid vehicles can be easily divided into two camps: those that you can plug-in to recharge the batteries, that those that solely rely on the vehicle’s engine and braking. The non-plug-in category can be further subdivided into those that can power the car’s engine and those that only power auxiliary systems (mild hybrids).

Most Hybrid vehicles have both an ICE and an electric motor that can power the vehicle. Regenerative braking is often used in hybrids to recoup energy lost from stopping the car. This is then stored, and diverted to power the car completely while idle, auxiliary systems while driving, and can help to boost power when faster acceleration is required. The extra energy captured from braking considerably increases the fuel efficiency of vehicles.

Plug-in Hybrid

Plug-in Hybrids often have larger batteries than other Hybrids, giving the car the ability to be driven completely by either the ICE or the electric engine for long periods of time. Since around 99% of car trips are less than 80km (50 miles), a hybrid car can greatly reduce gasoline fuel use, with the ICE reserved for situations that require longer travel, reducing range anxiety.

The drawback here is the considerable amount of extra weight required to carry two engines, and two fuel types. Because of this, the performance of hybrid vehicles compared to either ICEs or electric vehicles of the same size is slightly compromised. Since battery costs are a large component of electric vehicles, this also saves on the cost of hybrid vehicles. With the ability to charge the battery at home at prices much lower than gasoline prices, hybrids are an excellent crossover vehicle while electric technology is advanced to become competitive with gasoline cars.

Electric

Full electric vehicles have an electric motor to power the car and a battery to store the electricity required. Battery sizes range from 30kWh in vehicles like the 2017 Nissan Leaf to 70kWh in larger-battery Tesla vehicles. Most newer models (2018+) have a large enough battery to

Electric vehicles have some compelling advantages over fossil fueled cars. Electric engines have considerably less delay in torque than gas cars, meaning the car moves as soon as you put the acceleration pedal down. Electric vehicles are also much quieter than gasoline cars, as the engine is not creating thousands of explosions a minute. However, most electric vehicles require considerable time to recharge, on the range of 20 minutes to hours. Most electric vehicles also have limited range. Even with ranges around 200 miles (340 km), this is considerably less than gasoline cars with 300+ miles of range (500+ km). For 2018, it is forecast that electric vehicles and plug-in hybrids will account for around 2% of all vehicle sales, with a total sales volume of around 2 million vehicles. While there are fewer electric vehicles on the road than CNG or LPG vehicles, their sales numbers are considerably higher.

Compressed Natural Gas (CNG)

The Compressed Natural Gas vehicle market currently comprises of about 26 million vehicles, with China having around 6 million, Iran 4.5 million, India 3 million, Pakistan 3 million, with Brazil and Argentina at 2 million apiece. Natural Gas is mainly comprised of methane (CH4). CNG vehicles require a second fuel tank to be installed, fuel delivery line, and a switch allowing the driver to choose between gasoline and CNG as the fuel. While most CNG vehicles suffer from slightly lowered engine power, and a shorter driving range on a single CNG tank, these vehicles do have lower emissions. CNG is also often a cheaper fuel per distance traveled, allowing the consumer to save on fuel prices.

These vehicles are used mostly in developing nations where cost is of greater concern than workmanship: poor quality tanks can lead to the vehicle explosions during collisions.

LPG / Autogas / Propane

According to the World LPG Gas Association, there are 25 million LPG vehicles currently in operation, with Turkey, Poland, and South Korea leading the world in its use. The composition of Autogas and Propane can vary slightly: Propane in North America is comprised of mainly propane molecules with three carbon atoms (C3H8), while Autogas in Europe can have up to 40% Butane mixed in, with four carbon atoms (C4H10). In the US, this is the same gas that is used for BBQ grills. Because LPG has a much higher fuel density than CNG, (25MJ/L versus 9MJ/L) and operates at a lower tank pressure (less than 2 MPa as a liquid while CNG is 20 – 25 MPa),  it is inherently safer and each tank can go farther. Because LPG is also retrofitted like CNG and used in tandem with gasoline, LPG-gasoline vehicles can reach refueling ranges of 1000 km. The vehicles normally start in gasoline mode, and can then be switched over to LPG mode when the engine has been heated. This is to ensure that the LPG fuel does not freeze when expanding in the pressure reducer.

Hydrogen

Hydrogen is not readily derived from a natural source like crude oil: it needs to be isolated. Often this is done using either electricity (electrolysis of water) or methane (steam-methane reforming), meaning that the fuel itself is only as clean as the process used to create it. There are also many other ways of producing hydrogen, including thermo-chemical production (using heat and chemicals), and directly from the sun. Hydrogen can be used as a fuel in two ways: burning it in an internal combustion engine or using a hydrogen fuel cell to produce electricity.

Hydrogen fuel cells (HFCVs)

Hydrogen fuel cell vehicles use fuel cells, typically proton-exchange membrane fuel cells, to produce an electric current, which then drives an electric motor. With over 36 hydrogen fueling stations in the US, there is a small market for these vehicles. Hydrogen fuel cell vehicles are more popular than Hydrogen ICE vehicles, and can have fuel cell efficiencies of up to 60%, leading to total efficiencies for the vehicles of around 50% – greater than the 25% for gasoline cars. HFCVs can also have long driving ranges, with ranges for vehicles like the Honda Clarity Fuel Cell Vehicle going up to 366 miles (589 km). December 2017, global sales for vehicles like the Toyota Mirai were 5,300: very low even when compared to Electric, CNG, or LPG vehicles.

Hydrogen ICE (HICEV)

Hydrogen can also be used as a fuel in ICE engines, with some cars lending themselves to only small modifications to allow hydrogen to burn. Some major manufacturers even tested prototypes of hydrogen ICE cars, like the 2005-2007 BMW Hydrogen 7. However, Hydrogen ICE engines are typically less efficient than HFCVs, meaning they are less compelling as a technology for powering cars.

Solar Power

Many solar power car competitions have been completed across across the world, with some vehicles reaching speeds of over 56 mph (91km/h). However many design considerations make these vehicles impractical for day to day use. Putting solar cells on cars does not provide enough area: a small solar cell collection can’t generate enough electricity to function as a good primary source. For cars like the Karma Revero, solar roofs on can add about 50 miles of charge in a month, which is hardly worth the time of installing the system. However for the car below, the Sono Sion, an average of an extra 6 miles / day (10km / day) can be added from its solar panels, going to around 18 miles (30km) a day in the summer months.

Sono Sion Prototype

Other sources of power

Human ingenuity has shown no bounds in how vehicles can be powered. However, some other methods are impractical, yet interesting that we have tried them:

  • Wood can be used as fuel if a gasifier is attached to the car. This became more popular during WWII when fuel was scarce.
  • Nuclear power looked to be harnessed in cars with the 1957 Ford concept car, the Nucleon.
  • Steam gas can be created using a boiler in a similar way to steam trains, and can be powered from coal, natural gas, or wood.
  • Liquid nitrogen expands when it boils, and this expansion can fire pistons
  • Ammonia (NH3) has a calorific value of calorific value of ammonia is 22.5 MJ/kg (9690 BTU/lb) – about half that of diesel fuel – and can be burned in existing gasoline cars with some modifications. It can be made from green sources similar to hydrogen.

Conclusion

While gasoline is still the main source of fuel for cars, fuel sources are becoming more diversified as more electric, hybrid, CNG, and LPG vehicles are being added to the mix. As battery technology becomes more economical, the near future will bring cost parity between electric and gasoline cars.