O               
                        
O       Oxygen                                 氧
O       Off                                    關,離開
O-RING  O-Ring                                 O環
O.A.    Overall                                總,全
O.D     Outside Diameter                       外徑
O.N.    Octane Number                          辛烷值
O.S.    Off Side                               遠側(司機居左時為右側)
O.T.    Oil Tight                              不漏油
O/D     Over Drive                             超速傳動
O/S     Over Size                              加大尺寸
OAL     Overall Length                         全長,總長
OAPEC   Organixation of the Arab Petroleum
        Exporting Countries                    阿拉伯石油輸出國機構
OASIS   On-Line Automotive Service Information
        System                                 線上汽車服務資訊系統
OBC     On-Board Computer                      隨車電腦,車上電腦
OBD     On-Board Diagnostics                   自我診斷
OC      Oxidation Catalyst                     氧化觸媒
OC      Oil Consumption                        潤滑油消耗量
OC      Open Chamber                           開式燃燒室
OCC     Output Circuit Check                   輸出線路檢查
OCS     Oxidizing Catalytic Converter System   氧化觸媒轉換器系統
OCT ADJ Octane Adjust                          辛烷值調整
OCT.    Octane Number                          辛烷值
OCV     Oil Control Valve                      機油控制閥
OD      Outside Diameter                       外徑
OD      Origin to Destination                  起點到終點,全程
OD      Outer Diameter                         外徑
ODEC    Overdrive Engagement Control           超速嚙合控制
ODI     Oil Drain Intervals                    機油更間隔時間
ODO     Odometer                               里程表
OE      Opposed-Cylinder Engine                對置氣缸發動機
OH      Overhaul                               大修
OH.     Overhang                               外懸(包括前懸和後懸)
OHC     Over Head Camshaft                     頂上凸輪軸式
OHC     Overhead Camshaft                      頂置凸輪軸
OHV     Overhead Valve                         頂置氣門
OI      Overdrive Inhibit                      超速抑制
OL      Open Loop                              開環,開路
OLTBI   Open Loop Throttle-body Fuel Injector
        (system)                               開路控制節氣門區汽油噴射系統
ON      Octance Number                         辛烷值
ONR     Octane Number Rating                   辛烷值
ONR     Octane Number Requirement              辛值要求
OP-KARMAN       Optical karman Voltices Air
                 Flow Meter                    光學式卡門渦流式空氣流量計
OPEC    Organization of Petroleum Exporting 
        Countries                              石油輸出國機構
Oper    Operated                               動作,操作
Opt     Options or Optional                    選擇位置,選擇性
OR      Octane Requirements                    辛烷值要求
OR      Overload Relay                         超載繼電器
ORG     Orange                                 桔色
OS      Oxygen Sensor                          含氧感測器
OS      Over Size                              大於標準尺寸
OS      Over Steer                             過度轉向
OSAD    Orifice Spark Advance Control System   細孔點火提前真空控制系統
OSC     Output State Check                     輸出狀態檢查
OTCS    Over-Temperature Control System        超溫(過熱/冷)控制系統
OTS     Oil Temperature Switch                 機油壓力開關
OVV     Outer Vent Valve                       (三菱)外通氣閥
OWC     One Way Clutch                         單向離合器
OX1     Oxygen Sensor1                         含氧感測器#1
OX2     Oxygen Sensor2                         含氧感測器#2
OX3     Sub-Oxygen Sensor3                     副含氧感測器#3
OXD     Oxidation Catalyst                     氧化催化劑
OXS     Oxygen  Sensor                         含氧感測器
OZ      Ounce                                  盎司
OZ SENSOR       Oxygen Sensor                  氧感測器