Diesel Mechanics

Home | Diesel Engines | Basic Maintenance + Repair

QUICK FACTS about this job:

  • School Subjects: Computer science, Math, Technical/shop
  • Personal Skills: Following instructions, Mechanical/manipulative
  • Work Environment: Mostly indoors, Primarily one location
  • Minimum Education Level: High school diploma
  • Salary Range: $24,370 to $45,000 to $55,890+
  • Certification or Licensing: Recommended
  • Outlook: About as fast as the average
  • DOT: 625
  • GOE: 05.03.01
  • NOC: 7335
  • O*NET-SOC: 49-3031.00


Diesel mechanics repair and maintain diesel engines that power trucks, buses, ships, construction and road-building equipment, farm equipment, and some automobiles. They may also maintain and repair non-engine components, such as brakes, electrical systems, and heating and air-conditioning units. Approximately 275,000 diesel mechanics work in the United States.


In 1892, Rudolf Diesel patented an engine that, despite its weight and large size, was more efficient than the gasoline engine patented by Gottlieb Daimler less than a decade earlier. While Daimler’s engine became the standard for automobiles, Diesel found his engine had practical use for industry. The diesel engine differs from the gasoline engine in that the ignition of fuel is caused by compression of air in the engine’s cylinders rather than by a spark. Diesel’s engines were eventually used to power pipelines, electric and water plants, automobiles and trucks, and marine craft. Equipment used in mines, oil fields, factories, and transoceanic shipping also came to rely on diesel engines. With the onset of World War I, diesel engines became standard in submarines, tanks, and other heavy equipment. Suddenly, diesel mechanics were in big demand and the armed forces established training programs. Combat units supported by diesel-powered machines often had several men trained in diesel mechanics to repair breakdowns. The war proved to the industry that diesel engines were tough and efficient, and many companies found applications for diesel-powered machines in the following years.

At the turn of the century, trucks were wooden wagons equipped with gasoline engines. As they became bigger, transported more goods, and traveled farther, fuel efficiency became a big concern. In 1930, the trucking industry adopted the diesel engine, with its efficiency and durability, as its engine for the future. Many diesel mechanics began their training as automobile mechanics, and learned diesel through hands-on experience. World War II brought a new demand for highly trained diesel mechanics, and again the armed forces trained men in diesel technology. After the war, diesel mechanics found new jobs in diesel at trucking companies that maintained large fleets of trucks, and at construction companies that used diesel-powered equipment. It wasn’t until the 1970s that diesel engines in consumer passenger cars began to gain popularity. Before then, the disadvantages of diesel—its heaviness, poor performance, and low driving comfort—made diesel a second choice for many consumers. But the fuel crisis of the 1970s brought diesel a greater share of the automotive market, creating more demand for mechanics who could repair and maintain diesel engines.

Today, job growth and security for diesel mechanics is closely tied to the trucking industry. In the 1980s and 1990s, the trucking industry experienced steady growth as other means of transportation, such as rail, were used less frequently. Now, many businesses and manufacturers have found it cost efficient to maintain less inventory. Instead, they prefer to have their materials shipped on an as-needed basis. This low-inventory system has created a tremendous demand on the trucking industry, and diesel mechanics are essential to helping the industry meet that demand.


Most diesel mechanics work on the engines of heavy trucks, such as those used in hauling freight over long distances, or in heavy industries such as construction and mining. Many are employed by companies that maintain their own fleet of vehicles. The diesel mechanic’s main task is preventive maintenance to avoid break downs, but they also make engine repairs when necessary. Diesel mechanics also frequently perform maintenance on other non-engine components, such as brake systems, electronics, transmissions, and Suspensions.

Through periodic maintenance, diesel mechanics keep vehicles and engines in good operating condition. They run through a check list of standard maintenance tasks, such as changing oil and filters, checking cooling systems, and inspecting brakes and wheel bearings for wear. They make the appropriate repairs or adjustments and replace parts that are worn. Fuel injection units, fuel pumps, pistons, crankshafts, bushings, and bearings must be regularly removed, reconditioned, or replaced.

As more diesel engines rely on a variety of electronic components, mechanics have become more proficient in the basics of electronics. Previously technical functions in diesel equipment (both engine and non-engine parts) are being replaced by electronics, significantly altering the way mechanics perform maintenance and repairs. As new technology evolves, diesel mechanics may need additional training to use tools and computers to diagnose and correct problems with electronic parts. Employers generally provide this training.

Diesel engines are scheduled for periodic rebuilding usually every 18 months or 100,000 miles. Mechanics rely upon extensive records they keep on each engine to determine the extent of the rebuild. Records detail the maintenance and repair history that helps mechanics determine repair needs and prevent future break downs. Diesel mechanics use various specialty instruments to make precision measurements and diagnostics of each engine component. Micrometers and various gauges test for engine wear. Ohmmeters, ammeters, and voltmeters test electrical components. Dynamometers and oscilloscopes test overall engine operations.

Engine rebuilds usually require several mechanics, each specializing in a particular area. They use ordinary hand tools such as ratchets and sockets, screwdrivers, wrenches, and pliers; power tools such as pneumatic wrenches; welding and flame-cutting equipment; and machine tools like lathes and boring machines. Diesel mechanics typically supply their own hand tools at an investment of $6,000 to $25,000, depending upon their specialty. It is the employer’s responsibility to furnish the larger power tools, engine analyzers, and other diagnostic equipment.

In addition to trucks and buses, diesel mechanics also service and repair construction equipment such as cranes, bulldozers, earth moving equipment, and road construction equipment. The variations in transmissions, gear systems, electronics, and other engine components of diesel engines may require additional training.

To maintain and increase their skills and to keep up with new technology, diesel mechanics must regularly read service and repair manuals, industry bulletins, and other publications. They must also be willing to take part in training programs given by manufacturers or at vocational schools. Those who have certification must periodically retake exams to keep their credentials. Frequent changes in technology demand that mechanics keep up-to-date with the latest training.


High School

A high school diploma is the minimum requirement to land a job that offers growth possibilities, a good salary, and challenges. In addition to automotive and shop classes, high school students should take mathematics, English, and computer classes. Adjustments and repairs to many car components require the mechanic to make numerous computations, for which good mathematical skills will be essential. Diesel mechanics must be voracious readers to stay competitive; there are many must-read repair manuals and trade journals. Computer skills are also important, as computers are common in most repair shops.

Postsecondary Training

Employers prefer to hire those who have completed some kind of for mal training program in diesel mechanics, or in some cases automobile mechanics—usually a minimum of two years’ education in either case. A wide variety of such programs are offered by community colleges, vocational schools, independent organizations, and manufacturers. Most accredited programs include periods of internship.

Some programs are conducted in association with truck and heavy equipment manufacturers. Students combine work experience with hands-on classroom study of up-to-date equipment provided by manufacturers. In other programs students alternate time in the classroom with internships at manufacturers. Although these students may take up to four years to finish their training, they become familiar with the latest technology and also earn modest salaries as they train.

Certification or Licensing

One indicator of quality for entry-level mechanics recognized by everyone in the industry is certification by the National Institute for Automotive Service Excellence. There are eight areas of certification available in medium/heavy-duty truck repair: gasoline engines; diesel engines; drivetrain; brakes; suspension and steering; electrical/electronic systems; heating, ventilation, and air conditioning; and preventive maintenance inspection. There are seven areas of certification available in school bus repair: body systems and special equipment, diesel engines, drivetrain, brakes, suspension and steering, electrical/electronic systems, and air-conditioning systems and controls. Applicants must have at least two years of experience in the field and pass the examinations related to their specialty. To maintain their certification, mechanics must retake the examination for their specialties every five years. The Association of Diesel Specialists also offers voluntary certification to diesel mechanics.

cif-automotive-96.jpg A mechanic repairs a diesel engine.

Other Requirements

Diesel mechanics must be patient and thorough in their work. They need to have excellent troubleshooting skills and must be able to logically deduce the cause of system malfunctions. Diesel mechanics also need a Class A driver’s license.


Many community centers offer general auto maintenance workshops where students can get additional practice working on real cars and learn from instructors. Trade magazines such as Land Line (http:// www.landlinemag.com) and Overdrive (http://www.overdriveonline.com) are excellent sources for learning what’s new in the trucking industry and can be found at libraries and some larger bookstores. Working part time at a repair shop or dealership can prepare students for the atmosphere and challenges a mechanic faces on the job.

Many diesel mechanics begin their exploration on gasoline engines because spare diesel engines are hard to come by for those who are just trying to learn and experiment. Diesel engines are very similar to gasoline engines except for their ignition systems and size. Besides being larger, diesel engines are distinguished by the absence of common gasoline engine components such as spark plugs, ignition wires, coils, and distributors. Diesel mechanics use the same hand tools as automobile mechanics, however, and in this way learning technical aptitude on automobiles will be important for the student who wishes to eventually learn to work on diesel engines.


Diesel mechanics may find employment in a number of different areas. Many work for dealers that sell semi trucks and other diesel- powered equipment. About 17 percent of the country’s 275,000 diesel mechanics work for local and long-distance trucking companies. Others maintain the buses and trucks of public transit companies, schools, or governments or service buses, trucks, and other diesel- powered equipment at automotive repair and maintenance shops, motor vehicle and parts wholesalers, or automotive equipment rental and leasing agencies. Diesel mechanics can find work all over the country, in both large and small cities. Job titles may range from bus maintenance technician to hydraulic system technician, clutch rebuilder, and heavy-duty maintenance mechanic. A small number of diesel mechanics may find jobs in the railway and industrial sectors and in marine maintenance.


The best way to begin a career as a diesel mechanic is to enroll in a postsecondary training program and obtain accreditation. Trade and technical schools nearly always provide job placement assistance for their graduates. Such schools usually have contacts with local employers who need to hire well-trained people. Often, employers post job openings at accredited trade schools in their area.

Although postsecondary training programs are more widely avail able and popular today, some mechanics still learn the trade on the job as apprentices. Their training consists of working for several years under the guidance of experienced mechanics. Trainees usually begin as helpers, lubrication workers, or service station attendants, and gradually acquire the skills and knowledge necessary for many service or repair tasks. However, fewer employers today are willing to hire apprentices because of the time and cost it takes to train them. Those who do learn their skills on the job inevitably require some formal training if they wish to advance and stay in step with the changing industry.

Intern programs sponsored by truck manufacturers or independent organizations provide students with opportunities to actually work with prospective employers. Internships can provide students with valuable contacts who will be able to recommend future employers once students have completed their classroom training. Many students may even be hired by the company for which they interned.


Typically the first step a mechanic must take to advance is to receive certification. Although certification is voluntary, it is a widely recognized standard of achievement for diesel mechanics and the way many advance. The more certification a mechanic has, the more his or her worth to an employer, and the higher he or she advances.

With today’s complex diesel engine and truck components requiring hundreds of hours of study and practice to master, more employers prefer to hire certified mechanics. Certification assures the employer that the employee is skilled in the latest repair procedures and is familiar with the most current diesel technology. Those with good communication and planning skills may advance to shop supervisor or service manager at larger repair shops or companies that keep large fleets. Others with good business skills go into business for themselves and open their own shops or work as freelance mechanics. Some master mechanics may teach at technical and vocational schools or at community colleges.


Diesel mechanics’ earnings vary depending upon their region, industry (trucking, construction, railroad), and other factors. According to the U.S. Department of Labor, the median hourly pay for all diesel mechanics in 2006 was $18.11, or approximately $37,660 annually, for full-time employment; the lowest paid 10 percent of diesel mechanics earned approximately $11.71 an hour, or $24,370 a year, while the highest paid 10 percent earned more than $26.50 an hour, amounting to $55,120 a year. Mechanics who work for companies that must operate around the clock, such as bus lines, may work at night, on weekends, or on holidays and receive extra pay for this work.

The highest paid diesel mechanics work in motor vehicle manufacturing. They earned a mean hourly wage of $26.87 an hour, or $55,890 a year, in 2006. Those who worked for general freight trucking companies earned a mean hourly wage of $17.19, or $35,760 a year, and those who specialized in automotive repair and maintenance earned an average of $17.79 an hour, or $37,000 a year.

Many diesel mechanics are members of labor unions, and their wage rates are established by contracts between the union and the employer. Benefits packages vary from business to business. Mechanics can expect health insurance and paid vacation from most employers. Other benefits may include dental and eye care, life and disability insurance, and a pension plan. Employers usually cover a mechanic’s work clothes through a clothing allowance and may pay a percentage of hand tools purchases. An increasing number of employers pay all or most of an employee’s certification training if he or she passes the test. A mechanic’s salary can increase by yearly bonuses or profit sharing if the business does well.


Depending on the size of the shop and whether it is a trucking or construction company, government, or private business, diesel mechanics work with anywhere from two to 20 other mechanics. Most shops are well lighted and well ventilated. They can be frequently noisy due to running trucks and equipment. Hoses are attached to exhaust pipes and led outside to avoid carbon monoxide poisoning.

Minor hand and back injuries are the most common problem for diesel mechanics. When reaching in hard-to-get-at places or loosening tight bolts, mechanics often bruise, cut, or burn their hands. With caution and experience most mechanics learn to avoid hand injuries. Working for long periods of time in cramped or bent positions often results in a stiff back or neck. Diesel mechanics also lift many heavy objects that can cause injury if not handled cautiously; however, most shops have small cranes or hoists to lift the heaviest objects. Some may experience allergic reactions to the variety of solvents and oils frequently used in cleaning, maintenance, and repair. Shops must comply with strict safety procedures to help employees avoid accidents. Most mechanics work between 40- and 50-hour workweeks, but may be required to work longer hours when the shop is busy or during emergencies. Some mechanics make emergency repairs to stranded, roadside trucks or to construction equipment.


With diesel technology getting better (smaller, smarter, and less noisy), more light trucks, buses, and other vehicles (including some automobiles) and equipment are switching to diesel engines. Diesel engines are already more fuel efficient than gasoline engines. Also, the increased reliance by businesses for quick deliveries has increased the demand on trucking companies. Many businesses maintain lower inventories of materials, instead preferring to have items shipped more frequently. The increase in diesel-powered vehicles, together with a trend toward increased cargo transportation via trucks, will create jobs for highly skilled diesel mechanics. Less skilled workers will face tough competition. The U.S. Department of Labor predicts that employment will grow about as fast as the average for all occupations through 2016.

Diesel mechanics enjoy good job security. Fluctuations in the economy have little effect on employment in this field. When the economy is bad, people service and repair their trucks and equipment rather than replace them. Conversely, when the economy is good more people are apt to service their trucks and equipment regularly as well as buy new trucks and equipment.

The most jobs for diesel mechanics will open up at trucking companies who hire mechanics to maintain and repair their fleets. Construction companies are also expected to require an increase in diesel mechanics to maintain their heavy machinery, such as cranes, earthmovers, and other diesel-powered equipment.


For information on certification, contact

Association of Diesel Specialists

10 Laboratory Drive

P0 Box 13966

Research Triangle Park, NC 27709-3966

Tel: 919-406-8804

Email: info@diesel.org


For information on the automotive service industry and continuing education programs, contact

Automotive Aftermarket Industry Association

7101 Wisconsin Avenue, Suite 1300

Bethesda, MD 208 14-3415

Tel: 301-654-6664 Email: aaia@aftermarket.org


For information on training, accreditation, and testing, contact:


5125 Trillium Boulevard

Hoffman Estates, IL 60192-3600

Tel: 800-422-7872


For career information and information on certified programs, contact:

National Automotive Technicians Education Foundation

101 Blue Seal Drive, Suite 101

Leesburg, VA 20175-5646

Tel: 703-669-6650


For information on becoming a certified mechanic, contact

National Institute for Automotive Service Excellence

101 Blue Seal Drive, Suite 101

Leesburg, VA 20175-5646

Tel: 888-ASE-TEST


For information on careers, visit

Automotive Careers Today



Rick Burnett is the coordinator of the Diesel Technology Program at Ashland Community and Technical College (http://www.ash land.kctcs.edu) in Ashland, Kentucky. He discussed the field below:

Q. Please tell us about your program and your background.

A. The program is certified by the National Automotive Technicians Education Foundation! National Institute for Automotive Service Excellence (ASE). It is a two-year program including a 10-credit summer term depending on the path taken. We offer two associate of applied science/general occupational technical studies degrees—one in construction equipment technology and the other in medium/heavy truck technician. We also offer diplomas in these areas and in farm machinery technician along with 12 certificates. The program covers all aspects of repair (powertrain, engines, antilock brake systems (ABS), electrical, steering and suspension, hydraulics, preventive maintenance, and troubleshooting). There are two instructors in our program. I am an ASE master certified auto and medium/heavy truck technician, but my main background is construction equipment as I worked on strip mining for about 14 years and have been teaching about 21 years. The other instructor, Shannon McCarty, has about 14 years of experience with trucks and construction equipment and has his certification in medium/heavy truck.

Q. What is one thing that young people may not know about a career in diesel technology?

A. This can be a very rewarding career. We often see technicians making in excess of $ 100,000. We have moved into the computer age where everything on the trucks and equipment is computer controlled (i.e., engine controls, ABS brakes, load- sensing steering, and transmission controls). There is a short age of trained technicians, and it is only getting worse. Large shops are recruiting electricians, automotive technicians, and others to try to keep up with the need for technicians.

Q. What types of students pursue study in your program?

A. Most of the students who do well in this career are those who like to work with their hands. They need to have good math skills and be able to read for information and comprehend the material to repair today’s equipment. We get a lot of students from agriculture, welding, and automotive programs.

Q. What advice would you offer diesel technology majors as they graduate and look for jobs?

A. The construction equipment field pays better than the truck field, but you can make good money in either. Students need to do what they like and not worry as much about the money. There are plenty of opportunities in either field.

Q. What is the employment outlook in the field?

A. There is a shortage of technicians and a lot more are close to retirement age. Anyone willing to work in this field can make a good living with some job security. The shops around here are stealing the better techs by offering better money so it looks good for the younger people coming into the market.

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