Question 1

Vapor lock is caused by fuel that does not vaporize easily in hot weather.

Accepted Answer

Vapor lock is caused by fuel vaporizing too easily in the fuel lines, usually due to high temperatures, which prevents liquid fuel from reaching the engine.

Question 2

Technician A says a lean mixture burns faster than a rich mixture. Technician B says advanced ignition timing induces knock. Who is correct?

Accepted Answer

B

Question 3

The diesel fuel's antiknock quality is measured by the cetane rating.

Accepted Answer

The cetane rating measures the combustion quality of diesel fuel during compression ignition, indicating its antiknock properties. Higher cetane numbers mean the fuel ignites more readily under compression, leading to smoother engine operation and less knocking.

Question 4

The octane rating has nothing to do with fuel economy or engine efficiency.

Accepted Answer

The octane rating measures a fuel's ability to resist knocking during combustion, not its efficiency or economy.

Question 5

Pump gasoline may safely contain up to 10 percent alcohol.

Accepted Answer

Many gasoline blends contain up to 10 percent ethanol (a type of alcohol) to oxygenate the fuel, which helps reduce air pollution. This is commonly referred to as E10 and is considered safe for use in all gasoline engines.

Question 6

LP-gas delivers more power than gasoline.

Accepted Answer

LP-gas (Liquefied Petroleum Gas) has a lower energy density compared to gasoline, meaning that for the same volume, gasoline delivers more energy and thus more power to an engine.

Question 7

LNG (liquefied natural gas)is not a practical fuel for personal use and is only used in heavy-duty applications.

Accepted Answer

The answer of LNG (liquefied natural gas)is not a practical...

Question 8

A gasoline engine provides more torque at lower speeds than an electric motor.

Accepted Answer

Electric motors can provide maximum torque from a standstill, whereas gasoline engines develop their maximum torque within a specific range of engine speeds, not at the lowest speeds.

Question 9

Octane ratings are being discussed. Technician A says most modern engines are designed to use regular grade gasoline. Technician B says to use high octane gasoline only when an engine was designed to use it. Who is correct?

Accepted Answer

Most modern engines are indeed designed to run on regular grade gasoline, which is what Technician A states. However, there are engines, particularly high-performance engines, that require or benefit from high octane gasoline to prevent knocking and to operate efficiently. Technician B's advice to use high octane gasoline only when an engine is designed for it is also correct, as using high octane fuel in an engine not designed for it offers no benefit and can be more expensive. Therefore, both technicians are correct.

Question 10

Oxygenated fuels tend to have higher CO emissions.

Accepted Answer

Oxygenated fuels are designed to burn more completely, thereby reducing carbon monoxide (CO) emissions.

Question 11

Because diesel engines burn less fuel, they also emit less CO₂.

Accepted Answer

Diesel engines burn fuel more efficiently than gasoline engines, resulting in lower CO₂ emissions.

Question 12

The most widely used gasoline oxygenate additive is ethanol (ethyl alcohol).

Accepted Answer

Ethanol is commonly used as an oxygenate additive in gasoline to increase octane and reduce carbon monoxide and other emissions, making it the most widely used gasoline oxygenate.

Question 13

Ethanol decreases CO emissions due to the higher oxygen content of the fuel.

Accepted Answer

Ethanol contains oxygen, which allows for a more complete combustion of the fuel, resulting in lower carbon monoxide (CO) emissions compared to conventional gasoline.

Question 14

Compressed natural gas (CNG)is the cleanest alternative fuel.

Accepted Answer

CNG is a cleaner alternative fuel compared to traditional fossil fuels like gasoline and diesel, as it produces fewer emissions and pollutants.

Question 15

The octane number is a measure of a fuel's ability to produce power.

Accepted Answer

The octane number is a measure of a fuel's ability to resist knocking or pinging during combustion, not directly its ability to produce power.

Question 16

The ideal air/fuel or stoichiometric ratio for a gasoline engine is approximately _____ pounds of air mixed with 1 pound of gasoline.

Accepted Answer

The ideal air/fuel or stoichiometric ratio for a gasoline engine is approximately 14.7 pounds of air mixed with 1 pound of gasoline. This ratio allows for complete combustion of the fuel, optimizing efficiency and reducing emissions.

Question 17

All the following are factors that cause knock EXCEPT:

Accepted Answer

Decreased compression ratio actually reduces the likelihood of knock, as it lowers the pressure and temperature in the combustion chamber, making it less likely for the fuel-air mixture to detonate prematurely.

Question 18

The higher the octane rating of gasoline, the more the engine will have a tendency to knock.

Accepted Answer

A higher octane rating in gasoline actually reduces the likelihood of engine knocking because it is more resistant to pre-ignition under high pressure and temperature conditions in the engine's combustion chamber.

Question 19

Piezoelectric materials can emit a small amount of voltage when they are struck, squeezed, or exposed to vibration.

Accepted Answer

Piezoelectric materials generate an electric charge in response to applied mechanical stress, such as being struck, squeezed, or exposed to vibration.

Question 20

Biomass fuels are those derived from nonfossil sources and produced from plant or animal 
products or wastes.

Accepted Answer

Biomass fuels are indeed derived from nonfossil sources, specifically from organic materials such as plant or animal products or wastes, making them a renewable energy source.

Quiz 28: Gasoline, Diesel and Other Fuels