| Opel Straight-6 | |
| Aka: | Vauxhall Straight-6 |
| Manufacturer: | Opel |
| Production: | 1930-1966 |
| Successor: | Opel CIH engine |
| Configuration: | Naturally aspirated Straight-6 |
| Valvetrain: | OHV 2 valves x cyl. |
| Fueltype: | Petrol |
| Fuelsystem: | Carburetor |
| Coolingsystem: | Water-cooled |
| Displacement: | 1790cc 2605cc |
| Bore: | 652NaN2 852NaN2 |
| Stroke: | 902NaN2 76.52NaN2 |
| Power: | NaNPS |
| Torque: | NaN0NaN0 |
| Compression: | 7.8:1 |
Opel used the straight-6 engine configuration for many years. Opel used two straight-6 engines prior to the better-known CIH engine family.
The Opel Moonlight roadster was the first Opel vehicle with a straight-6. It used a 1790cc six in 1933. It was a 12-valve engine with a very-undersquare NaN2NaN2 bore and stroke, typical for the time. This engine produced 33.5PS and 1000NaN0.
The 1959 Opel Kapitän was the next vehicle from the company with a straight-6 engine. This was a 2605cc unit with 12 overhead valves. Bore and stroke were now oversquare for high power output at NaNmm. A single Opel-designed carburetor and 7.8:1 compression yielded 910NaN0 and 1860NaN0.