Diesel service technicians and mechanics inspect, repair, or overhaul buses, trucks, and anything else with a diesel engine.


Diesel service technicians and mechanics typically do the following:

  • Follow a checklist of inspection procedures
  • Test drive vehicles to diagnose malfunctions
  • Read and interpret diagnostic test results from diagnostic equipment such as an oscilloscope, which is used to measure the voltage produced by electronic components
  • Raise trucks, buses, and heavy parts or equipment by using hydraulic jacks or hoists
  • Inspect brake systems, steering mechanisms, transmissions, engines, and other parts of vehicles
  • Do routine maintenance, such as changing oil, checking batteries, and lubricating equipment and parts
  • Adjust and align wheels, tighten bolts and screws, and attach system components
  • Repair or replace malfunctioning components, parts, and other mechanical or electrical equipment
  • Test-drive vehicles to ensure that they run smoothly

Because of their efficiency and durability, diesel engines have become the standard in powering our nation’s trucks and buses. Other heavy vehicles and mobile equipment, including bulldozers and cranes, also are powered by diesel engines, as are many commercial boats, passenger vehicles, pickups, and other work trucks. Diesel service technicians who service and repair these engines are commonly known as diesel mechanics.

Diesel mechanics handle many kinds of repairs. They may work on a vehicle’s electrical system, make major engine repairs, or retrofit exhaust systems with emission control systems to comply with pollution regulations.

Diesel engine maintenance and repair is becoming more complex as engines and other components use more electronic systems to control their operation. For example, fuel injection and engine timing systems rely heavily on microprocessors to maximize fuel efficiency and minimize harmful emissions. In most shops, workers often use hand-held or laptop computers to diagnose problems and adjust engine functions. 

In addition to using computerized diagnostic equipment, diesel mechanics use a variety of power and machine tools, such as pneumatic wrenches, lathes, grinding machines, and welding equipment. Hand tools, including pliers, socket and ratchets, and screwdrivers, are commonly used.

Employers typically provide expensive power tools and computerized equipment, but workers generally acquire their own hand tools over time.

For information on technicians and mechanics who work primarily on automobiles, see the profile on automotive service technicians and mechanics.

For information on technicians and mechanics who work primarily on farm equipment, construction vehicles, and rail cars, see the profile on heavy vehicle and mobile equipment service technicians.

For information on technicians and mechanics who work primarily on motorboats, motorcycles, and small all-terrain vehicles, see the profile on small engine mechanics.

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Work Environment

Diesel service technicians and mechanics held about 250,800 jobs in 2012. The majority worked for private companies, but about 10 percent worked for the government.

The industries that employed the most diesel service technicians and mechanics in 2012 were as follows:

Truck transportation 18%
Government 10
Repair and maintenance 9
Motor vehicle and motor vehicle parts and supplies merchant wholesalers 8
Manufacturing 5

Diesel mechanics usually work in well-ventilated and sometimes noisy repair shops. They occasionally repair vehicles on roadsides or at worksites.

Injuries and Illnesses

Diesel service technicians and mechanics have a higher rate of injuries and illnesses than the national average. Diesel mechanics often lift heavy parts and tools, handle greasy or dirty equipment, and work in uncomfortable positions. Although cuts or burns are common, the work is generally not hazardous when workers follow basic safety precautions.

Work Schedules

Most diesel mechanics work full time. Overtime is common as many repair shops extend their service hours during evenings and weekends. In addition, some truck and bus repair shops provide 24-hour maintenance and repair services.

Education and Training

Many diesel mechanics learn informally on the job, but employers increasingly prefer applicants who have completed postsecondary training programs in diesel engine repair. Although not required, industry certification can be important for diesel mechanics.


Most employers require a high school diploma or equivalent. High school or postsecondary courses in automotive repair, electronics, and mathematics provide a strong educational background for a career as a diesel mechanic.

Many employers look for workers with postsecondary training in diesel engine repair. A large number of community colleges and trade and vocational schools offer programs in diesel engine repair that may lead to a certificate of completion or an associate’s degree.

Programs mix classroom instruction with hands-on training, including the basics of diesel technology, repair techniques and equipment, and practical exercises. Students also learn how to interpret technical manuals and electronic diagnostic reports.

Graduates usually advance to journeyworker status, where they may then work with minimal supervision.


Some diesel mechanics begin working without postsecondary education and are trained on the job. Trainees are assigned basic tasks, such as cleaning parts, checking fuel and oil levels, and driving vehicles in and out of the shop.

After they learn routine maintenance and repair tasks and demonstrate competence, trainees move on to more complicated jobs. This process can last from 3 to 4 years, at which point a trainee is usually considered a journey-level diesel mechanic.

Over the course of their careers, diesel mechanics must learn new techniques and learn about new equipment. Employers often send experienced mechanics to special training classes conducted by manufacturers and vendors to learn about the latest diesel technology.

Licenses, Certifications, and Registrations

Certification from the National Institute for Automotive Service Excellence (ASE) is the recognized industry credential for diesel and other automotive service technicians and mechanics. Although not required, this certification represents a diesel mechanic’s competence, experience, and value to potential employers and clients.

Diesel mechanics may be certified in specific repair areas, such as drive trains, electronic systems, or preventative maintenance and inspection. To earn certification, mechanics must have 2 years of work experience and pass one or more ASE exams. To remain certified, diesel mechanics must pass the test again every 5 years.

Some diesel mechanics may be required to have a commercial driver’s license if their job duties include test-driving buses or large trucks.

Personality and Interests

Diesel service technicians and mechanics typically have an interest in the Building and Organizing interest areas, according to the Holland Code framework. The Building interest area indicates a focus on working with tools and machines, and making or fixing practical things. The Organizing interest area indicates a focus on working with information and processes to keep things arranged in orderly systems.

If you are not sure whether you have a Building or Organizing interest which might fit with a career as a diesel service technician and mechanic, you can take a career test to measure your interests.

Diesel service technicians and mechanics should also possess the following specific qualities:

Customer-service skills. Diesel mechanics frequently talk to their customers about automotive problems and work that they have planned, started, or completed. They must be courteous, good listeners and ready to answer customers’ questions.

Dexterity. Mechanics need a steady hand and good hand-eye coordination for many tasks, such as disassembling engine parts, connecting or attaching components, or using hand tools.

Mechanical skills. Diesel mechanics must be familiar with parts and components of engines, transmissions, braking mechanisms, and other complex systems. They must also be able to disassemble, work on, and reassemble parts and machinery.

Troubleshooting skills. Diesel mechanics must be able to identify mechanical and electronic problems, make repairs, and offer a proper maintenance strategy. They must be familiar with electronic control systems and the appropriate tools needed to fix and maintain them.


The median annual wage for diesel service technicians and mechanics was $42,320 in May 2012. The median wage is the wage at which half the workers in an occupation earned more than that amount and half earned less. The lowest 10 percent earned less than $26,820, and the top 10 percent earned more than $63,250.

In May 2012, the median annual wages for diesel service technicians and mechanics in the top five industries in which these technicians and mechanics worked were as follows:

Government $49,130
Motor vehicle and motor vehicle parts and supplies
merchant wholesalers
Manufacturing 42,160
Repair and maintenance 38,880
Truck transportation 38,250

Many diesel mechanics, especially those employed by truck fleet dealers and repair shops, receive a commission in addition to their base salary. 

Most diesel mechanics work full time. Overtime is common as many repair shops extend their service hours during evenings and weekends. In addition, some truck and bus repair shops provide 24-hour maintenance and repair services.

Job Outlook

Employment of diesel service technicians and mechanics is projected to grow 9 percent from 2012 to 2022, about as fast as the average for all occupations.

As more freight is shipped across the country, additional diesel-powered trucks will be needed. As a result, diesel mechanics will be needed to maintain and repair the nation’s truck fleet. Demand for new workers in the freight trucking and automotive repair and maintenance industries is expected to drive overall diesel mechanic job growth.

Some older vehicles will need to be retrofitted and modernized to comply with environmental regulations, creating additional jobs for diesel mechanics.

Overall employment growth, however, may be dampened due to increasing durability of new truck and bus diesel engines. Also, continuing advances in repair technology, including computerized diagnostic equipment, will result in fewer mechanics doing the same amount of work, further reducing demand for mechanics.

Job Prospects

Job opportunities should be good for those who have completed formal postsecondary education and have strong technical skills, as employers sometimes report difficulty finding qualified workers.

Workers without formal training often require more supervision and on-the-job instruction than others—an expensive and time-consuming process for employers. Because of this, untrained candidates will face strong competition for jobs.

For More Information

For more information about careers and education for diesel service technicians and mechanics, visit

Association of Diesel Specialists

National Automotive Technicians Education Foundation

For information about certification, visit

National Institute for Automotive Service Excellence


Where does this information come from?

The career information above is taken from the Bureau of Labor Statistics Occupational Outlook Handbook. This excellent resource for occupational data is published by the U.S. Department of Labor every two years. Truity periodically updates our site with information from the BLS database.

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There are many excellent tools available that will allow you to measure your interests, profile your personality, and match these traits with appropriate careers. We recommend the Career Personality Profiler assessment ($29), the Holland Code assessment ($19), or the Photo Career Quiz (free).

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