name - The name that will appear above the top line of the infobox. If it is the name of a specific locomotive, then it should be in italics, as per WP:ITALIC, e.g. |name = ''Mallard''.
image - The filename for the infobox image. Use the bare image name, i.e. |image=Example.jpg not |image=[[File:Example.jpg]]
alt - alternative text for the image, displayed when the image cannot be shown (such as for visually impaired users, or for spoken articles)
imagesize - The size of the image in pixels (as in imagesize= 200), default value is 300; to use the image's actual size, specify imagesize as a blank value (as in imagesize= |).
caption - The image caption that will be displayed
hatnote - A label-less centered text field for notices. Appears below powertype.
powertype - The type of power that the locomotive employs (e.g. "Steam", "Diesel", "Diesel-electric", "Electro-diesel", "Electric", etc.)
designer - The name of the locomotive's designer
builder - The locomotive builder
ordernumber - The locomotive's order number(s)
serialnumber - The locomotive's serial number(s)
buildmodel - The builder's model number
builddate - The date(s) that the locomotive (or locomotive model) was built. Use {{Start date}} (and {{End date}} where applicable).
totalproduction - The total number of locomotives of the given class that were built
rebuilder - The locomotive rebuilder
rebuilddate - The date(s) that the locomotive (or locomotive model) was rebuilt
numberrebuilt - The total number of locomotives of the given class that were rebuilt
engine total - The engine's wheelbase, tender excluded
leading - The wheelbase of the leading truck/bogie
drivers - USA terminology: The wheelbase of the driving wheels
coupled - British terminology: The wheelbase of the coupled wheels
trailing - The wheelbase of the trailing truck/bogie
truck - USA terminology: The wheelbase of each truck on diesels and electrics
bogie - British terminology: The wheelbase of each bogie on diesels and electrics
tender total - The wheelbase of the tender
tendertruck - USA terminology: The wheelbase of each tender truck
tenderbogie - British terminology: The wheelbase of each tender bogie
pivotcentres - Garratts, diesels and electrics: distance between engine unit or bogie pivot centres
pantoshoecentres - Electrics: distance between pantograph shoe centres
wheelspacing - To describe trucks/bogies or coupled wheels with asymmetrical wheel spacing
length - The locomotive's total length, tender included
over couplers - The length between the coupler faces
over bufferbeams - The length between the buffer beams
body - The length of the locomotive body (diesels and electrics)
width - The locomotive's total width
height - The locomotive's total height
pantodown - An electric locomotive's height, including pantographs in the stowed position
body - An electric locomotive's body height, discounting the pantographs
frametype - The type of locomotive frame (e.g. "Plate frame", "Bar frame" or "Cast frame")
axleload - maximum axle load (average, or the load on the axle(s) which carry the greatest load)
leadingbogie/pony - The load on the leading bogie or pony axle
coupled all - Use when the load on all coupled wheels are the same
coupled 1 - The load on the 1st coupled axle
coupled 2 - The load on the 2nd coupled axle
coupled 3 - Etc.
coupled 4
coupled 5
coupled 6
coupled 7
coupled 8
trail bogie/pony - The load on the trailing bogie or pony axle
tenderbogieload - The axle load per tender bogie - use |tenderbogieload=Bogie 1: [data]<br>Bogie 2: [data] or |tenderbogieload=Truck 1: [data]<br>Truck 2: if different
tenderaxle - The axle load per individual tender axle - use tenderaxle=Axle 1: {{convert|...}}<br>Axle 2:, etc
weightondrivers - The weight on the driven wheels only
locoweight - The weight of the locomotive in working order (excluding tender)
tenderweight - The weight of the locomotive's tender in working order
locotenderweight - The combined weight of the locomotive and tender in working order
tendertype - The type of tender; typically the number of axles, the designer, or (where issued), the class of tender
fueltype - The type of fuel that the locomotive consumes
fuelcap - The locomotive's full fuel capacity
lubecap - Lubrication oil capacity
coolantcap - Engine coolant capacity
watercap - The tender's full water capacity
tendercap - The tender's full fuel and water capacity
sandcap - The locomotive's full sandbox capacity
consumption - The locomotive's average fuel consumption rate
watercons - The locomotive's average water consumption rate
powersupply - Head-end power; the electric power supplied to the train by the locomotive
electricsystem - The electric system(s) under which the locomotive operates (e.g. 3 kVDC, Dual 3 kVDC & 25 kV AC 50 Hz, etc.)
maxspeed - The locomotive's maximum permitted speed
poweroutput - The locomotive's total power output
poweroutput start - The locomotive's starting motor rating
poweroutput 1 hr - The locomotive's one hour motor rating
poweroutput cont - The locomotive's continuous motor rating
tractiveeffort - The locomotive's total tractive effort
t/e starting - The locomotive's starting tractive effort
t/e 1 hr - The locomotive's one hour tractive effort
t/e continuous - The locomotive's continuous tractive effort
acceleration - The locomotive's rate of acceleration (with a stated load)
deceleration - The locomotive's rate of deceleration (with a stated load)
factorofadhesion - Factor of adhesion (weight on drivers divided by tractive effort)
f/adh starting - The locomotive's starting factor of adhesion
f/adh 1 hr - The locomotive's one hour factor of adhesion
f/adh continuous - The locomotive's continuous factor of adhesion
operator - The operator(s) (railroad/railway/industry/company) who used the locomotive (for articles about individual locomotives and not generic locomotive models)
operatorclass - The class designation assigned by the locomotive’s operator
powerclass - The power class or group of the locomotive
numinclass - The number of locomotives in the same railroad/railway/industry/company class
fleetnumbers - The operating number(s) assigned by the operator
officialname - The official name(s) assigned by the operator, and who or what the locomotive is named after
framesize - The size of the locomotive frame - replaced by frametype - the type of locomotive frame (e.g. "Plate frame", "Bar frame" or "Cast frame")
weight - The weight of the locomotive (may or may not have included a tender) – replaced by locoweight, tenderweight, and locotenderweight
leadingsize - The size of the locomotive's leading wheels – replaced by leadingdiameter
driversize - The size of the locomotive's driving wheels – replaced by driverdiameter
trailingsize - The size of the locomotive's trailing wheels – replaced by trailingdiameter
topspeed - The locomotive's top speed – replaced by maxspeed
railroad - The operating railroad(s)/railway(s)/industry(ies) who used the locomotive – replaced by operator
railroadclass - The class designation assigned by the operating railroad – replaced by operatorclass
roadnumber - The operating number(s) assigned by the railroad – replaced by fleetnumbers
The examples above are for a generic diesel-electric locomotive model (EMD GP30), a specific steam locomotive (John Bull) and a 1-C+C-1 electric locomotive (South African Class 4E).