| GA | Gravitational Acceleration |
| GDI | Gasoline Direct Injection |
| GE | General Electric |
| GEN | Generator |
| GEO | Gas Engine Oil |
| GF-2/3 | Passenger car motor oil classifications (ILSAC) prior to 2004 |
| GF-4 | Passenger car motor oil classification (ILSAC) from 2004 through Sept 30, 2011 |
| GF-5 | Passenger car motor oil classification (ILSAC) first licensed Oct 1, 2010 |
| GFC | Groupement Français de Coordination |
| GL-4/5 | Gear service characteristics (API) |
| GM | General Motors |
| GMOT | General Motors oxidation test |
| GO | Gear Oil |
| GO-J | Mack gear oil specification |
| GPA | Gasoline Performance Additives |
| GRPE | Groupe de Rapporteurs pour la Pollution et l’Energie |
| GT | Grand Turismo |
| GTAB | Gasoline Treated As Blend stock |
| GTL | Gas To Liquids |
| GVW | Gross Vehicle Weight |
