Michigan SOS mechanic test

Heavy-Duty Engine Repair – Gasoline

Heavy-Duty Engine Repair – Gasoline is one of the 20 Secretary of State mechanic certification tests. Here's what the test covers, according to the state's published outline.

Topic guide · questions soon

What's on the test

Official topicWeight
Engine mechanical diagnosis
  • Spark plug evaluation
  • Engine noise
  • Compression test
  • Oil consumption
  • Exhaust smoke color
  • Cylinder blocks
  • Cylinder heads
  • Piston rings
  • Overheating
26%
Skills in measuring
  • Torque angle
  • Measuring cylinder bore
  • Reading a micrometer
  • Reading a dial indicator
  • Reading Plastigage
  • How to check crankshaft end play
12%
Fundamentals
  • Electrical terms and definitions
  • Series / parallel circuits
  • Understanding how engines operate
  • Cooling system operation
  • Ignition systems
  • Camshaft timing
  • Fuel systems
31%
Electronic Controls
  • EGR operation
  • Variable valve timing
  • Sensor operation / diagnosis
  • Scan tool operation
  • EVAP system
32%

Weights are shown exactly as published by the SOS (they total 101%).

Source: SOS Mechanic Testing Categories Overview (PDF). Test format: most SOS mechanic tests have 55 questions, and a few have 65–100 (SOS FAQ). Passing scores vary by test; your result letter shows the passing score and your score.

Practice questions coming soon

The Heavy-Duty Engine Repair – Gasoline practice bank is being written to the official outline below. The All-Mechanic pass will include it when it launches.

Banks available now: Engine Repair · Front End, Suspension & Steering · Brakes & Braking Systems · Electrical Systems · Engine Tune-Up & Performance

Test-day facts

Source: michigan.gov/sos mechanic testing

Heavy-Duty Engine Repair – Gasoline test FAQ

How many questions are on the Michigan Heavy-Duty Engine Repair – Gasoline test?

The Secretary of State says most mechanic tests have 55 questions and a few have 65 to 100. The test is “quick pass,” so it ends as soon as you reach the minimum passing score.

What topics are on the Heavy-Duty Engine Repair – Gasoline test?

The SOS Mechanic Testing Categories Overview lists: Engine mechanical diagnosis (26%), Skills in measuring (12%), Fundamentals (31%), Electronic Controls (32%).

How much does the test cost, and where do I take it?

Each mechanic test costs $18 (effective July 1, 2026). Tests are taken on a touch-screen kiosk at any Secretary of State office; pre-register and schedule through SOS Online Services. Approved automotive schools can also test their students.

Are these the real test questions?

No. MI Trade Prep questions are original practice items written to the official topic outline. They are not actual exam questions, and MI Trade Prep is not affiliated with the Michigan Department of State.

Sources: SOS mechanic testing · SOS mechanics page · SOS mechanic FAQ