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Frances Perkins, S ecretary
Isador Lubin, C om m issioner (on leave)
A. F. Hinrichs, A c tin g C om m issioner

Employment Opportunities
for DiesehEngine

Bulletin T^o. 813
{Reprinted from the M onthly Labor R eview, February 1945]

For sale b y the Superintendent o f Docum ents, U . S. G overnm ent P rinting Office
W ashington 25, D . C . - Price 5 cents

Letter of Transmittal


n it e d

State s D

epartm ent of

u reau of



S t a t is t ic s ,

Washington,* D, C., February 28, 1945The S e c r e t a r y o f L a b o r :
I have the honor to transmit herewith a report on employment opportunities for
Diesel-engine mechanics. This is the first in a series of occupational studies
prepared in the Bureau’s Occupational Outlook Division for use in vocational
counseling of veterans, young people in schools, and others considering the
choice of an occupation. This study was prepared by Frank Dischel under
the supervision of Richard H. Lewis.

F rances P

F. H

in r ic h s ,

Acting Commissioner.

e r k in s ,

Secretary of Labor.

P age

Nature and importance of the occupation___________________ _____ ______
Characteristics of the Diesel engine---------------------- --------------------------------Prospects for expansion in use of Diesel engines_________________________
Opportunities for Diesel mechanics--------------------------------------------------------Training for Diesel maintenance---------------------------------

(n )


Bulletin T^o. 813 of the
U nited States Bureau o f Labor Statistics
[Reprinted from the M onthly L ab or R e v ie w , February 1945]

Employment Opportunities for Diesel-Engine
Sum m ary

The post-war demand for mechanics to service Diesel engines can be
adequately supplied from the relatively large number of experienced
engine mechanics who will be available. The value of Diesel training
for persons without mechanical experience is therefore definitely
limited. Experienced mechanics considering transferring to Diesel
maintenance, and mechanics already employed by firms using or
servicing such engines, may in some instances profit by brief training
courses to become familiar with the special characteristics of these
These are the chief conclusions drawn from an analysis of the
post-war labor market for Diesel mechanics, despite the rising trend
of sales of the engines in pre-war years and the favorable prospects
for a continued expansion of their utilization in the post-war period.
Although its importance is increasing, the Diesel engine now consti­
tutes and will probably continue to represent only a small proportion
of total engines in use. Because of its general similarity to other
internal-combustion engines, mechanics experienced in maintaining
other types of engines can transfer their skills to its servicing with
relatively little difficulty.
Companies replacing other types of engines with Diesel engines have
usually met their maintenance requirements by shifting mechanics
already employed in servicing the displaced engines, rather than by
hiring Diesel specialists. This employment policy is often reinforced
by the seniority provisions of labor contracts. In the situations in
which entirely new job openings result from the extension of Dieselengine use, mechanics experienced on other engines have generally
been preferred over inexperienced job applicants who have Diesel
N ature and Im portance o f the Occupation

In recent years the Diesel engine has been considered by many to
represent one of the outstanding new fields of employment oppor­
tunity opened by technical innovations. The relatively rapid expan­
sion jn the sales of Diesel engines during the decade of the 1930’s and
their adoption for new uses, such as with tractors, in trucks and in
busses, encouraged this view. Advertisements by schools offering


training stimulated interest in the vocational opportunities that
would be created by the increasingly wide acceptance of Diesel power.
The importance of these engines during the war, as measured by the
heavy requirements of the armed forces, has caused a renewed interest
in the post-war prospects for jobs in the Diesel field.
Information on the job openings that would be created by post­
war expansion in the use of these engines is needed by young people
without experience who are considering the value of this special
training in improving their employment opportunities, by mechanics
who wish to supplement their experience through courses in Diesel
maintenance, and by men who have been trained as Diesel mechanics
by the Army and Navy and who may want to adapt their wartime
experience to a peacetime vocation.
It is the purpose of this article to provide information leading to a
balanced judgment about employment opportunities for Diesel
mechanics. This information is based on interviews with manu­
facturers and users of these engines and with training-school officials,
as well as on an examination of the vocational and technical litera­
ture in the field.
In maintaining and repairing a Diesel engine, the mechanic per­
forms such duties as diagnosing trouble, disassembling the engine,
replacing or repairing defective parts, reassembling the engine, and
adjusting the fuel and air valves. The function of this mechanic is
similar to that of other engine mechanics, and Diesel-engine mainte­
nance is generally regarded as a specialized branch of general mechan­
ical work rather than as a separate and distinct occupation. Diesel
mechanics do not design or engage in the manufacture of the engine;
manufacturing occupations correspond to those found in the produc­
tion of other engines, and in metalworking and assembly operations
The term, “ Diesel engineer,” has been frequently used rather loosely
in vocational literature to refer sometimes to professional engineers
and sometimes to mechanics. The first Diesel engines were almost
exclusively of the heavy stationary and marine type and the latter
use of the term “ Diesel engineer” was carried over from the practice
of referring to maintenance men in power plants and on ships as
“ engineers.”
Diesel engineering, at the professional level, cannot be considered
to be a distinct occupation from the standpoint of either formal
educational requirements or practical specialization. The basic
required technical knowledge is that of the mechanical engineer.
Engineering colleges, for example, do not offer a degree in Diesel
engineering, although they may provide some courses in its principles
to mechanical-engineering students. Professional Diesel engineers
can probably be counted in the hundreds and are found primarily in
the manufacturing rather than the maintenance fields. The manu­
facture of Diesel engines requires the usual specialization of mechanical
engineering skills, including designers, research engineers, production
engineers, and installation engineers. As a result, the occupation of
Diesel engineering, in its restricted professional sense, can be in­
cluded both logically and practically under the broader occupational
title of mechanical engineer. This study considers only the Diesel

Diesel mechanics are employed in a wide range of industries in
vriiich Diesel engines are used. Some of the more important sources
of employment are ships and boats, public-utility and municipal
electric-power plants, stationary power plants in buildings and in
many manufacturing industries, logging, petroleum production, rail­
roads, and companies using or servicing Diesel busses, trucks, trac­
tors, construction machines, and earth-moving machinery.
Future needs for men who can service and repair Diesel engines
depend on the extent of the wider use of this engine in various indus­
tries. T o evaluate the prospects for increased Diesel utilization
requires an understanding of the characteristics of the engine and
recent trends in its introduction into important fields of use.
Characteristics o f the D iesel Engine

The Diesel engine has been able to compete successfully with existing
carburetor and steam engines for certain types of mechanical motive
power because of Its technical characteristics. It is an internal-com­
bustion engine, similar in structure to the gasoline (or carburetor)
engine. Both engines have similar stationary and working parts,
including crankcases, cylinders, cylinder blocks and heads, exhaust
manifolds and water-cooling systems with their associated pumps,
radiators, and circulation jackets.1 It is especially important to
recognize this similarity in structure, since one of the most important
factors in determining the opportunities for those with Diesel train­
ing is the ability of mechanics familiar with other engines to transfer
their skill to this type of engine.
The essential difference between the carburetor engine and the
Diesel engine, from the point of view of the mechanic, lies in their
different methods of ignition. The Diesel engine has no electric
ignition system and carburetor but has instead an oil-injector system
and fuel pumps, with which the mechanic must be familiar.
It can be operated more economically than other engines, in many
uses, because of its relatively more efficient utilization of fuel. This
and certain other technical advantages are offset by its higher initial
cost and greater weight per horsepower compared with the carburetor
engine. It also lacks the flexibility required for passenger automobiles
and is very noisy. These technical characteristics have made pos­
sible great expansions of its use in some fields, but have limited its use
in others.
Prospects fo r E xpansion in U se o f D iesel Engines

Employment opportunities in Diesel-engine maintenance occur in
the industries which use or service this type of engine. For this rea­
son it is important to measure the relative rate of introduction of the
Diesel engine into its various fields of use, as well as the total growth in
its production.
1 For a description of the structure of the Diesel engine see General M otors Corporation pamphlet,Diesel—
the M od em Power, published in 1941.

Much of the optimism concerning employment opportunities for
Diesel mechanics resulted from the wider use of the engines during
the decade before the war and their adaptation to new uses. Exami­
nation of the following tabulation2 shows the rapid recovery of Dieselengine production from the effects of the depression, and an expan­
sion well beyond previous high levels.
of units



Total rated

13,814 1,448,857



By 1935, the number of units produced, as well as their total rated
horsepower, exceeded the previous peak output of 1929. From 1933
to 1939 the number of units produced annually expanded 17 times,
the aggregate rated horsepower 14 times, and the total value nearly
9 times. During the decade there was a reduction in the average size
of the units produced, as measured by horsepower, and the average
price per horsepower was reduced by more than half. These changes
in character of output were caused mainly by the introduction of the
engine for new uses. Sales of Diesel engines had consisted almost
exclusively of marine and stationary engines until the early 1930,s,
when they began to be utilized in tractors, construction machinery,
and locomotives, which use smaller engines. By 1939 the production
of Diesel engines other than stationary and marine accounted for
over half of the units and about 43 percent of the total horsepower.
This does not include the engines made by tractor and locomotive
manufacturers for installation in their products.
Diesel-engine production not only increased absolutely, but also
made relative gains compared with carburetor engines (other than for
motor vehicles) and steam engines and turbines. Diesel-engine pro­
duction, as shown in the accompanying table, constituted 5.3 percent
of the aggregate rated horsepower of internal-combustion engines and
steam engines produced for sale as such in 1929, and 20.9 percent in
1939. However, the total production of engines included in this
comparison is only a small fraction of the production of carburetor
engines for passenger and commercial cars. There were 3,534,831
motor vehicles produced in 1939, including a very small number of
Diesel-powered trucks and busses, while only 19,263 Diesel-engine
units were made in independent engine plants (where the greater part
of their production takes place). In addition, 478,935 carburetor
engines were produced for other purposes, including 141,154 marine
engines and 32,663 tractor engines.3 Although Diesel-engine pro­
duction has shown a marked relative as well as an absolute increase
since 1929, it has begun to enter the market for motor-vehicle engines
only in trucks and busses, and in these only to a small extent.
* Data are from the Census of Manufactures. T hey exclude all aircraft and motor-vehicle engines and
engines made for installation in Diesel-electric locomotives, ships, boats, or tractors, when the engines in the
locom otives, etc., are built b y the same establishment.
3 Census of Manufactures, 1939.

During the war a tremendous increase in Diesel-engine production
has taken place, to meet the requirements of the armed forces. The
total for 1943 has been estimated at 25,000,000 horsepower, as com­
pared with less than 2,000,000 horsepower produced in 1939. The
wartime output has exceeded the aggregate horsepower produced
from the beginning of manufacture in this country through 1941.
The greater part of the wartime production has gone directly to the
armed forces, with the Navy taking the largest share. These engines
have been used so extensively in such vessels as submarines, destroyers,
patrol boats, and landing boats that the Diesel horsepower operated
by the Navy is greater than its total steam horsepower. The Army
has used Diesels in some of its tanks and heavy trucks, and both
services have relied upon them to power the construction and earthmoving equipment which has been so important during the war.
Distribution of Engine Production by Type of Engine, 1929 and 19391
Rated horsepower

T yp e of engine




A ll types...................................................................................




Diesel engines *......................................................................
Carburetor engines (excluding those used in motor
vehicles)3. . ......................... ..................................................
Steam engines and turbines3...............................................










3 Census of Manufactures.
* Data for Diesel engines and carburetor engines exclude all motor-vehicle and aircraft engines, as well
as engines made for installation in locomotives, ships, boats, or tractors, when the engines are made b y the
establishment building the locomotives, etc.
3 Data for steam engines and steam turbines exclude production of locomotives and turbo-generators, and
steam engines made for installation as parts of ships, blowers, pumps, etc., when the engines are made b y
the establishment building the ships, etc.

The post-war prospects for Diesel-engine sales, after war contracts
have been terminated, depend upon the ability of the manufacturers
to compete in the normal peacetime markets for engines. The high
production levels of the war have made possible the development of
mass-production methods and have stimulated technical improve­
ments which may aid the competitive position of the Diesel engine.
Before the war this type of engine had been used in many different
industrial fields, but until recently was particularly important as a
source of stationary and marine power. The following tabulation
shows the distribution of installed Diesel horsepower at the end of
1941 by type of use. The categories listed have been.grouped under
the kind of Diesel engine typically utilized by each.

(thousands) *

All types________ ____ ___ _____ . . . _______ ______ 19, 122


100. 0

Tractors and co n tra cto r machinery, includ­
ing tanks______________ _________ _______



6, 247

32. 6
2 .2

General industry___________________________
Public utility_________________ - ................. ..
Municipal light and water_________ _________

6, 594

34. 6
26. 9
2. 8
4. 9

Marine, including U. S. Navy___________________
Railroads__________ :____________________________

3, 841
1, 057

20. 1
5. 5

i Data are from Diesel Power, January 1942.

The magnitude of post-war sales will depend upon the success of
Diesel manufacturers in maintaining and extending their previous
gains in the marine and power fields and developing further their
market for locomotive- and automotive-type engines, including those
for trucks, busses, praetors, and construction and farm machinery.
Diesel engines will be utilized extensively in ships and boats, particu­
larly in the medium- and small-size vessels.
The use of Diesel and Diesel-electric locomotives by the railroads
will undoubtedly continue to expand. By 1943 over 2,000 Diesel
locomotives were being operated by class l railroads, most of which
had been purchased since 1937. Their relatively minor place in this
field is indicated by the fact that more than 40,000 steam locomotives
are also in service. Railroads have used the greatest number of their
Diesel locomotives for switching, and they may largely supersede
steam locomotives in this function. Many lines have been operating
the widely publicized Diesel-electric streamlined passenger trains,
and in the past few years Diesel locomotives have been successfully
introduced into freight service.
In recent years a large proportion of the tractors and construction
machinery produced have been powered by Diesel engines, and it is
probable that they will continue to dominate this field in the post-war
The automotive field constitutes by far the greatest market for
engines. Diesel trucks and busses are now in use, but they are still
a very small proportion of the total. There are good prospects for
expansion in the truck and bus field, however, particularly in the
heavier vehicles, and especially if technical improvements reduce the
present disadvantages of Diesels for this type of use. It is considered
unlikely that Diesel engines will be used in passenger cars in the pre­
dictable future.

Job opportunities for Diesel mechanics are related to the number
of Diesel engines in use. There were at least 100,000 units in service
at the end of 1939. More recent data on the number of units pro­
duced are not available, but statistics on the rated horsepower of
engines produced since 1939 for nonmilitary use suggest that the
number of units in service may now be at least 50 percent higher than
in 1939. The post-war period may see a substantial increase over pre­
war levels in the utilization of these engines if some of the sales poten­
tialities listed above are realized and if many of the Diesel engines
constructed during the war are used for peacetime purposes. Under
these conditions the number in use should more than double the 1939
total within a few years after the war, and it will probably continue
to increase at a rapid rate.
Opportunities fo r D iesel Mechanics

The wider use of Diesel engines in the marine, electric-power, rail­
road, and automotive fields after the war will result in an increased
need for maintenance. However, this greater demand will not re­
quire a corresponding increase in the supply of newly trained Diesel
mechanics, because of the ease with winch mechanics familiar with
other types of engines can transfer their skill to the maintenance of
Diesel engines.
Employment practices among the industries using these engines
largely determine the number of new job openings for Diesel mechan­
ics as the engines are introduced and the need for their servicing
arises. Large electric power stations, for example, generally employ
supervisory stationary engineers with long practical experience who
are directly responsible for the operation, maintenance, and repair of
engines, and mechanics are usually placed under their immediate
supervision. When a Diesel engine replaces another engine, the
stationary engineer must apply ms experience and previous knowl­
edge to the new engine and then retrain the mechanics under his
Officers in charge of the operation and maintenance of the engines
on ships are also called engineers, and they must be licensed by the
U. S. Bureau of Marine Inspection and Navigation in peacetime and
by the U. S. Coast Guard during the war. Their duties are somewhat
broader than those of the stationary engineer because they are respon­
sible for the operation and maintenance of all of the mechanical and elec­
trical equipment on a ship. In the requirements for engineers' licenses,
experience in the engine department of ships weighs very heavily, and a
written examination must also be passed. A person with Diesel training
but without engine-department experience on ships is not sufficiently
qualified for even the lowest grade of licensed engineer, even though
the requirements have been reduced during the war. Separate li­
censes are provided for engineers on steam and Diesel ships, and an
engineer on a steam vessel cannot obtain a license for a Diesel (motor)
vessel until he has acquired experience in the engine department of a
Diesel ship. This requirement has been waived during the war, for
third assistant engineers, and steam and Diesel experience are inter­
changeable for this, the lowest grade of licensed engineer.

The adoption of Diesel engines by railroads usually involves a
readjustment by their experienced mechanics rather than the hiring
of new personnel. The explanation was made, during an interview
with an official of a large railroad company, that the seniority rules
of their labor contract required that the mechanics employed in the
maintenance of steam locomotives be assigned to Diesel engines before
new workers are hired. Since the mechanics on this railroad had
undergone an apprenticeship of 4 years and usually had long
practical experience, they were considered able to repair a Diesel
engine with little formal supervision or retraining.
More recently, employment opportunities for Diesel mechanics
have appeared in the servicing of motor vehicles. The experience of
a large bus company, with 40 percent of its busses powered by Diesels,
may be cited as one example of employment practices in the automo­
tive field. The manager of the maintenance department reported
that all the mechanics who had been hired had only gasoline-engine
experience, even though a large number of busses with Diesel engines
had been serviced for several years. When Diesel engines were
originally introduced, the bus company selected several foremen and
superior mechanics and sent them to a Diesel training school for 2
months. These trainees- then served as leadmen in training other
mechanics. Mechanics with Diesel training or experience had not
been hired recently, simply because none had been available on account
of the wartime shortage of skilled engine mechanics. It is significant
that the company was able to make its adjustment to Diesel-engine
busses by depending primarily on the skill of its gasoline mechanics.
It is evident that the wider use of Diesel engines has generally
resulted in the retraining and adaptation of the skills of engine me­
chanics who were already employed rather than in their technological
displacement. Experience or training in servicing Diesel engines may
improve the competitive position of an engine mechanic in the labor
market, but length of experience, seniority, and all-round mechanical
ability will continue to be the more important considerations even if
Diesel engines should replace other forms of motive power.
The supply of qualified Diesel mechanics has been augmented by
the large number of servicemen who have received Diesel training
during the war. The Navy established a special rating for Diesel
mechanics, known as “ motor machinist's mate,” in January 1942. On
September 1 , 1944, there were 70,364 motor machinist's mates, in­
cluding 54,900 who had been trained as Diesel mechanics since the
start of the war. The Army also trained 5,086 enlisted men as Diesel
mechanics during a similar period. The Navy has trained mechanics
to service marine Diesel engines, while the Army has generally
trained Diesel mechanics to maintain tank and truck engines.
No data are available as to the number of experienced Diesel
mechanics and the number of Diesel-school graduates. The number
of these mechanics employed cannot be easily determined, since many
of their employers' records do not show a separate occupation for
them and many also work on other engines. Although no statistics
are available, there is evidence that the number of resident Dieselschool students has been very small dining the war.
However, if past practices are followed by employers, most of the
job openings created by the wider use of Diesel engines will be filled

by mechanics employed in repairing other engines. The 1940 Census
of Population reported 949,658 persons experienced as mechanics and
repairmen, represented by 441,845 automobile, 28,384 airplane, and
43,998 railroad mechanics and repairmen, as well as by 435,431 other
mechanics and repairmen. While the number of engine mechanics,
as distinct from other types of mechanics and repairmen, cannot be
specifically determined, most of the 514,227 automobile, airplane, and
railroad mechanics and repairmen were probably engine mechanics,
and many engine mechanics can be found among the 435,431 other
mechanics and repairmen. This large reservoir of men, capable of
learning to maintain and repair Diesels with relatively little additional
training because of their previous experience, is the greatest single
factor in the potential supply of Diesel mechanics.
The relative position of Diesel engines as a source of demand for
repairmen is indicated by the fact that only about 100,000 Diesel
engines were in use by the end of 1939, as compared to 31,000,000
registered passenger cars and motor trucks using carburetor engines.
Although, as suggested above, the number of Diesel engines to be
serviced may double the 1939 total within a few years after the war
and continue to grow, it will still represent only a small fraction of the
number of other types of engines in use.
The practice of retraining mechanics experienced on other engines
to service Diesel engines, before new workers are engaged, and the
increased supply of Diesel mechanics trained in the armed forces
make the potential supply of Diesel mechanics after the war more
than sufficient to meet any demand that may reasonably be expected.
As a result, the value of Diesel training for persons without experience
in engine maintenance would seem to be definitely limited. Experi­
enced mechanics who desire to transfer to Diesel maintenance, and
mechanics already employed by companies using or servicing Diesels,
may find brief training courses useful in learning about some of the
specialized components of the Diesel, such as the oil injector and
fuel pump.
Training fo r D iesel M aintenance

In cases in which it has been decided that training would aid in
obtaining or holding a job in Diesel maintenance, the training course
should be carefully selected. There are no generally recognized stand­
ards for Diesel training, and in any event the scope of the instruction
would depend upon the previous mechanical knowledge of the student.
Privately operated trade schools offering Diesel training have often
provided inadequate facilities and instruction. Before enrolling in a
privately operated trade school, the prospective student may be able
to obtain information on the quality of the instruction offered, from
the superintendent of schools or the director of vocational training
in the locality in which the school operates.
Courses in Diesel mechanics are taught in, a number of public
vocational and trade schools operated by local school boards. Gener­
ally this training is given as a part of regularly conducted training in
auto mechanics. Special courses in maintenance can frequently be
made available by vocational schools for employed adults who re­
quire Diesel training in connection with their daily employment.

Information on opportunities for training in this field may be obtained
from the local superintendent of schools or the local director of voca­
tional education.
Correspondence courses seem to be of little practical value to the
person without mechanical experience, although they may be helpful
to the experienced engine mechanic if he is able to learn from textual
materials without the direct personal guidance of an instructor.
Two complete although accelerated training programs for Diesel
mechanics were conducted by the Army and Navy. The Army pro­
gram involved 12 weeks of training as an automobile mechanic and
an additional 4 weeks of specific Diesel training, for a total of 800
hours of study. The Navy has required an 8-week preliminary
engineering course and a 5-week elementary Diesel course, followed by
4 to 8 weeks of advanced Diesel-engine training, or a total of 850 to
1,050 hours of study. These training programs were designed to be
complete courses of study, suitable for students with little practical
experience, the specific Diesel-engine training being viewed either as
part of the broader training of a competent engine mechanic or as an
extension of previous training as an auto- or marine-engine mechanic.
These military training programs were designed for a specific
purpose, the supplying of qualified Diesel maintenance men to the
armed forces— and are interesting as an illustration rather than as a
model for a civilian course of instruction. In peacetime mechanical
training the scope and content of the course of study selected should
be consistent with the background and needs of the individual student.

I). S . G O V E R N M E N T P R IN T IN G O F F I C E : 1 9 4 *