NYC DCAS Auto Mechanic Exam-Practice
Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A |
Instant Download Pdf
1. What is the primary purpose of engine oil?
A. Increase fuel pressure
B. Lubricate moving components and reduce friction
C. Cool the passenger compartment
D. Increase battery voltage
Answer: B
Rationale: Engine oil lubricates moving parts, reduces friction and wear, helps carry heat away,
and suspends contaminants for removal by the oil filter.
2. What does the viscosity rating of engine oil describe?
A. Its electrical resistance
B. Its resistance to flow
C. Its freezing point only
D. Its detergent concentration
Answer: B
Rationale: Viscosity describes a fluid's resistance to flow. Multi-grade oils are formulated to
provide suitable viscosity over a range of temperatures.
3. What is the function of an oil filter?
A. Remove contaminants from engine oil
B. Increase oil temperature
C. Regulate coolant pressure
D. Filter fuel from the tank
Answer: A
Rationale: The oil filter removes suspended contaminants from engine oil before the oil
circulates through engine components.
, 4. What is the most common cause of low engine oil pressure?
A. Excessive tire pressure
B. Low oil level or excessive bearing clearance
C. A fully charged battery
D. A clean air filter
Answer: B
Rationale: Low oil level reduces available oil, while excessive bearing clearance can allow oil
pressure to escape too readily.
5. What is the purpose of engine coolant?
A. Lubricate brake pads
B. Transfer heat and prevent freezing and corrosion
C. Increase fuel octane
D. Clean fuel injectors
Answer: B
Rationale: Coolant transfers heat from the engine to the radiator and provides freeze and
corrosion protection.
6. What component regulates coolant flow through the engine?
A. Thermostat
B. Alternator
C. Starter
D. Fuel injector
Answer: A
Rationale: The thermostat controls coolant flow to maintain the engine within its intended
operating temperature range.
7. A thermostat stuck open will commonly cause:
A. Rapid overheating
B. Slow engine warm-up
C. Excessive brake pressure
D. High battery voltage
Answer: B
Rationale: A thermostat stuck open allows coolant to circulate continuously, often preventing
the engine from reaching normal operating temperature.
, 8. What is the purpose of a radiator?
A. Store engine oil
B. Transfer coolant heat to surrounding air
C. Generate electrical current
D. Control fuel pressure
Answer: B
Rationale: The radiator dissipates heat from engine coolant into the surrounding air.
9. What can a damaged radiator cap cause?
A. Incorrect system pressure and coolant loss
B. Increased tire wear
C. Low alternator output
D. Reduced brake pad thickness
Answer: A
Rationale: The radiator cap maintains cooling-system pressure and controls coolant expansion
and recovery.
10. What is the primary function of the alternator?
A. Start the engine
B. Produce electrical power while the engine runs
C. Control transmission gears
D. Compress refrigerant
Answer: B
Rationale: The alternator supplies electrical power to vehicle systems and recharges the battery
while the engine operates.
11. What component stores electrical energy for starting and other electrical needs?
A. Alternator
B. Battery
C. Starter relay
D. Voltage regulator
Answer: B
Rationale: The battery stores electrical energy and supplies high current to the starter during
engine cranking.
, 12. What is the purpose of the starter motor?
A. Rotate the engine during starting
B. Cool the transmission
C. Regulate fuel pressure
D. Operate the radiator fan
Answer: A
Rationale: The starter motor turns the engine crankshaft until combustion can sustain engine
operation.
13. A clicking sound during starting with no engine rotation may indicate:
A. A discharged battery or poor electrical connection
B. Excessive coolant level
C. A clogged cabin filter
D. A worn tire
Answer: A
Rationale: Repeated clicking can occur when the starter solenoid engages but insufficient
current is available because of a weak battery or high-resistance connection.
14. What does a fuse protect?
A. The engine from overheating
B. An electrical circuit from excessive current
C. Tires from overinflation
D. Brake fluid from contamination
Answer: B
Rationale: A fuse opens the circuit when current exceeds its designed rating, helping protect
wiring and components.
15. Why should a blown fuse be replaced with the correct rating?
A. A larger fuse always improves performance
B. The specified rating protects the wiring and circuit
C. It increases battery capacity
D. It improves tire traction
Answer: B
Rationale: Installing an oversized fuse can allow excessive current to flow and potentially
damage wiring or cause a fire.
Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A |
Instant Download Pdf
1. What is the primary purpose of engine oil?
A. Increase fuel pressure
B. Lubricate moving components and reduce friction
C. Cool the passenger compartment
D. Increase battery voltage
Answer: B
Rationale: Engine oil lubricates moving parts, reduces friction and wear, helps carry heat away,
and suspends contaminants for removal by the oil filter.
2. What does the viscosity rating of engine oil describe?
A. Its electrical resistance
B. Its resistance to flow
C. Its freezing point only
D. Its detergent concentration
Answer: B
Rationale: Viscosity describes a fluid's resistance to flow. Multi-grade oils are formulated to
provide suitable viscosity over a range of temperatures.
3. What is the function of an oil filter?
A. Remove contaminants from engine oil
B. Increase oil temperature
C. Regulate coolant pressure
D. Filter fuel from the tank
Answer: A
Rationale: The oil filter removes suspended contaminants from engine oil before the oil
circulates through engine components.
, 4. What is the most common cause of low engine oil pressure?
A. Excessive tire pressure
B. Low oil level or excessive bearing clearance
C. A fully charged battery
D. A clean air filter
Answer: B
Rationale: Low oil level reduces available oil, while excessive bearing clearance can allow oil
pressure to escape too readily.
5. What is the purpose of engine coolant?
A. Lubricate brake pads
B. Transfer heat and prevent freezing and corrosion
C. Increase fuel octane
D. Clean fuel injectors
Answer: B
Rationale: Coolant transfers heat from the engine to the radiator and provides freeze and
corrosion protection.
6. What component regulates coolant flow through the engine?
A. Thermostat
B. Alternator
C. Starter
D. Fuel injector
Answer: A
Rationale: The thermostat controls coolant flow to maintain the engine within its intended
operating temperature range.
7. A thermostat stuck open will commonly cause:
A. Rapid overheating
B. Slow engine warm-up
C. Excessive brake pressure
D. High battery voltage
Answer: B
Rationale: A thermostat stuck open allows coolant to circulate continuously, often preventing
the engine from reaching normal operating temperature.
, 8. What is the purpose of a radiator?
A. Store engine oil
B. Transfer coolant heat to surrounding air
C. Generate electrical current
D. Control fuel pressure
Answer: B
Rationale: The radiator dissipates heat from engine coolant into the surrounding air.
9. What can a damaged radiator cap cause?
A. Incorrect system pressure and coolant loss
B. Increased tire wear
C. Low alternator output
D. Reduced brake pad thickness
Answer: A
Rationale: The radiator cap maintains cooling-system pressure and controls coolant expansion
and recovery.
10. What is the primary function of the alternator?
A. Start the engine
B. Produce electrical power while the engine runs
C. Control transmission gears
D. Compress refrigerant
Answer: B
Rationale: The alternator supplies electrical power to vehicle systems and recharges the battery
while the engine operates.
11. What component stores electrical energy for starting and other electrical needs?
A. Alternator
B. Battery
C. Starter relay
D. Voltage regulator
Answer: B
Rationale: The battery stores electrical energy and supplies high current to the starter during
engine cranking.
, 12. What is the purpose of the starter motor?
A. Rotate the engine during starting
B. Cool the transmission
C. Regulate fuel pressure
D. Operate the radiator fan
Answer: A
Rationale: The starter motor turns the engine crankshaft until combustion can sustain engine
operation.
13. A clicking sound during starting with no engine rotation may indicate:
A. A discharged battery or poor electrical connection
B. Excessive coolant level
C. A clogged cabin filter
D. A worn tire
Answer: A
Rationale: Repeated clicking can occur when the starter solenoid engages but insufficient
current is available because of a weak battery or high-resistance connection.
14. What does a fuse protect?
A. The engine from overheating
B. An electrical circuit from excessive current
C. Tires from overinflation
D. Brake fluid from contamination
Answer: B
Rationale: A fuse opens the circuit when current exceeds its designed rating, helping protect
wiring and components.
15. Why should a blown fuse be replaced with the correct rating?
A. A larger fuse always improves performance
B. The specified rating protects the wiring and circuit
C. It increases battery capacity
D. It improves tire traction
Answer: B
Rationale: Installing an oversized fuse can allow excessive current to flow and potentially
damage wiring or cause a fire.
