What the Auto & Shop Section Tests
The Auto & Shop Information (AS) section tests two related areas: automotive systems and basic shop tools/procedures. The CAT-ASVAB splits this into separate subtests — Auto Information (AI) and Shop Information (SI) — but they combine into a single AS score used in line score calculations.
AS feeds directly into Army MM (Mechanical Maintenance), GM (General Maintenance), and CO composites, as well as Air Force Mechanical (M). If you want a vehicle mechanic, maintenance, or technical MOS, a strong AS score is important. The paper ASVAB has 25 AS questions total.
Automotive Systems — Part 1: The Engine
The internal combustion engine is the most tested automotive topic. Know the 4-stroke cycle:
- Intake stroke — piston moves down, intake valve opens, air-fuel mixture enters cylinder
- Compression stroke — piston moves up, both valves closed, mixture compressed
- Power (combustion) stroke — spark plug fires, explosion drives piston down
- Exhaust stroke — piston moves up, exhaust valve opens, burned gases exit
Key engine components to know:
- Carburetor — mixes air and fuel (older vehicles); replaced by fuel injectors in modern cars
- Fuel injector — sprays precise fuel amount directly into cylinder
- Spark plug — ignites the air-fuel mixture in gasoline engines (diesel engines use compression, not sparks)
- Pistons — move up and down inside cylinders, converting combustion into mechanical motion
- Crankshaft — converts the up-down piston motion into rotational motion
- Camshaft — controls the timing of valve opening and closing
- Timing belt/chain — synchronizes the crankshaft and camshaft
- Alternator — generates electricity to charge the battery while the engine runs
- Starter motor — uses battery power to start the engine
Automotive Systems — Part 2: Supporting Systems
Cooling System
- Coolant (antifreeze) circulates through the engine to absorb heat
- Radiator — dissipates heat from the coolant into the air
- Thermostat — regulates coolant flow to maintain operating temperature
- Water pump — circulates the coolant
Lubrication System
- Engine oil — lubricates moving parts, reduces friction and heat
- Oil pump — forces oil through the engine
- Oil filter — removes contaminants from the oil
- Oil level should be checked with the dipstick when the engine is cold and on level ground
Electrical System
- Battery — stores electrical energy; provides power to start the car
- Alternator — recharges battery while the engine runs
- Fuses and circuit breakers — protect electrical circuits from overload
Braking System
- Disc brakes — a caliper squeezes brake pads against a rotating disc (rotor). More effective, used on front wheels of most cars.
- Drum brakes — brake shoes expand outward against the inside of a drum. Common on rear wheels.
- ABS (Anti-lock Braking System) — prevents wheel lockup during hard braking
- Hydraulic brake lines — transmit brake pedal force to the calipers/wheel cylinders
Transmission and Drivetrain
- Transmission — transfers engine power to the wheels; changes gear ratios
- Manual transmission — driver operates clutch and shifts gears manually
- Automatic transmission — shifts gears automatically using hydraulic torque converter
- Differential — allows wheels to spin at different speeds in turns
- Drive shaft — connects transmission to rear axle in rear-wheel drive vehicles
Shop Tools and Procedures
This part tests whether you can identify common hand tools and power tools and know their proper use:
Measuring Tools
- Micrometer — measures very small dimensions to thousandths of an inch
- Caliper — measures inside and outside dimensions
- Combination square — measures 90° and 45° angles; also measures length
- Tape measure / steel rule — standard length measurement
Cutting Tools
- Hacksaw — cuts metal
- Crosscut saw — cuts wood across the grain
- Rip saw — cuts wood along the grain
- Chisel — removes material by hand force
- File — removes small amounts of metal by abrasion; different cuts (bastard, second, smooth)
Fastening Tools
- Socket wrench / ratchet — tightens or loosens nuts/bolts using sockets
- Torque wrench — tightens fasteners to a specific torque specification
- Box-end wrench — surrounds the fastener completely (stronger than open-end)
- Open-end wrench — slides onto the fastener from the side (useful in tight spaces)
- Screwdrivers: flathead (slot), Phillips (cross), Torx (star)
Drilling and Grinding
- Drill press — more precise than handheld drill; used for exact-depth holes
- Twist drill bit — standard drill bit for metal and wood
- Bench grinder — sharpens tools, removes material
- Always clamp the workpiece — never hold it by hand when drilling
Shop Safety — Frequently Tested
- Always wear safety glasses when grinding, drilling, or cutting
- Never wear loose clothing or jewelry near rotating machinery
- Use hearing protection around loud equipment
- Disconnect power before changing blades or bits
- A fire involving electrical equipment should be extinguished with a Class C (CO₂ or dry chemical) extinguisher — never water
Study Approach for AS
AS is almost entirely memorization — there are no formulas to derive. The best approach:
- Use flashcards for tools — picture of the tool on one side, name and use on the other
- Learn the engine systems as stories — trace a drop of fuel or a drop of oil through the system start to finish
- Focus on the 4-stroke cycle — it generates multiple questions in almost every practice test
- Know disc vs. drum brakes and manual vs. automatic transmissions — common question topics
Use the Auto & Shop section drills to practice identifying tools and vehicle systems under timed conditions.