The Opel Commodore B 2.5, producing 115 horsepower, was a significant model within the Commodore B range, manufactured between 1972 and 1974. Positioned as a mid-range offering, it slotted between the base 2.2-liter models and the more potent 2.8-liter variants. The Commodore B, built upon the GM A-platform, represented Opel’s attempt to create a spacious, comfortable, and relatively affordable executive car for the European market. This generation saw a shift towards more modern styling and improved refinement compared to its predecessor, the Commodore A. The 2.5-liter version aimed to balance performance with fuel economy, appealing to buyers seeking a capable family saloon without the higher running costs of the larger-displacement engines.
Technical Specifications
| Brand | Opel |
| Model | Commodore |
| Generation | Commodore B |
| Type (Engine) | 2.5 (115 Hp) |
| Start of production | 1972 |
| End of production | 1974 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Sedan |
| Seats | 5 |
| Doors | 4 |
| Fuel Type | Petrol (Gasoline) |
| Acceleration 0 – 100 km/h | 13 sec |
| Acceleration 0 – 62 mph | 13 sec |
| Acceleration 0 – 60 mph | 12.4 sec |
| Maximum speed | 175 km/h (108.74 mph) |
| Weight-to-power ratio | 10.4 kg/Hp, 95.8 Hp/tonne |
| Weight-to-torque ratio | 6.9 kg/Nm, 145 Nm/tonne |
| Power | 115 Hp @ 5200 rpm |
| Power per litre | 46.2 Hp/l |
| Torque | 174 Nm @ 3800 rpm (128.34 lb.-ft. @ 3800 rpm) |
| Engine Model/Code | 25S |
| Engine displacement | 2490 cm3 (151.95 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | Inline |
| Cylinder Bore | 87 mm (3.43 in.) |
| Piston Stroke | 69.8 mm (2.75 in.) |
| Compression ratio | 9:1 |
| Number of valves per cylinder | 2 |
| Fuel injection system | Carburettor |
| Engine aspiration | Naturally aspirated engine |
| Valvetrain | SOHC |
| Engine oil capacity | 5.5 l (5.81 US qt | 4.84 UK qt) |
| Kerb Weight | 1200 kg (2645.55 lbs.) |
| Max. weight | 1640 kg (3615.58 lbs.) |
| Max load | 440 kg (970.03 lbs.) |
| Trunk (boot) space – minimum | 408 l (14.41 cu. ft.) |
| Fuel tank capacity | 70 l (18.49 US gal | 15.4 UK gal) |
| Length | 4607 mm (181.38 in.) |
| Width | 1728 mm (68.03 in.) |
| Height | 1405 mm (55.31 in.) |
| Wheelbase | 2668 mm (105.04 in.) |
| Front track | 1434 mm (56.46 in.) |
| Rear (Back) track | 1400 mm (55.12 in.) |
| Ride height (ground clearance) | 140 mm (5.51 in.) |
| Drag coefficient (Cd) | 0.46 |
| Minimum turning circle (turning diameter) | 11.2 m (36.75 ft.) |
| Drivetrain Architecture | The Internal combustion engine (ICE) drives the rear wheels of the vehicle. |
| Drive wheel | Rear wheel drive |
| Number of gears and type of gearbox | 4 gears, manual transmission |
| Front brakes | Disc |
| Rear brakes | Drum |
Powertrain & Engine Architecture
The heart of the Commodore B 2.5 was the 25S inline-six cylinder engine, displacing 2490cc (151.95 cubic inches). This engine utilized a single overhead camshaft (SOHC) valvetrain, operating two valves per cylinder. Fuel delivery was managed by a carburetor, a common setup for the era, rather than fuel injection. The 9:1 compression ratio was a typical value for gasoline engines of the time, balancing performance and fuel efficiency. The engine produced 115 horsepower at 5200 rpm and 174 Nm (128.34 lb-ft) of torque at 3800 rpm. The engine was mated to a four-speed manual transmission as standard, providing a relatively direct connection to the rear wheels. While an automatic transmission was offered on some Commodore B models, it wasn’t commonly paired with the 2.5-liter engine, making the manual version the more prevalent configuration.
Driving Characteristics
The 2.5-liter Commodore B offered a comfortable and relaxed driving experience. Acceleration was adequate, with a 0-60 mph time of around 12.4 seconds, but it wasn’t a particularly sporty car. The four-speed manual transmission provided reasonable control, but the engine’s torque peak at 3800 rpm meant that frequent shifting was necessary to maintain momentum, especially when overtaking. Compared to the 2.8-liter Commodore, the 2.5 felt noticeably less powerful, particularly at higher speeds. However, it offered better fuel economy and was generally considered more forgiving to drive. The rear-wheel-drive layout provided a balanced feel, although handling was not as sharp as more modern vehicles.
Equipment & Trim Levels
The Commodore B 2.5 typically came with a fairly standard level of equipment for a car of its class in the early 1970s. This included cloth upholstery, basic instrumentation (speedometer, fuel gauge, temperature gauge), and a heater. Optional extras included a radio, whitewall tires, and upgraded interior trim. The Commodore B was available in various trim levels, but the 2.5-liter version generally occupied a middle ground, offering a good balance of features and affordability. It wasn’t as lavishly equipped as the top-of-the-line models, but it wasn’t as spartan as the base versions either.
Chassis & Braking
The Commodore B utilized a traditional body-on-frame construction, providing a robust and durable chassis. The suspension consisted of independent front suspension with coil springs and a live axle rear suspension with leaf springs. Braking was accomplished via disc brakes on the front wheels and drum brakes on the rear. Steering was of the recirculating ball type, offering a relatively heavy but precise feel. The suspension setup prioritized ride comfort over sporty handling, resulting in a smooth and compliant ride, even on rough roads. The brake system, while adequate for the car’s weight and performance, lacked the stopping power of more modern braking systems.
Market Reception & Comparison
The Opel Commodore B 2.5 was generally well-received by automotive critics as a practical and comfortable family car. It was praised for its spacious interior, smooth ride, and relatively affordable price. However, it was also criticized for its somewhat dated styling and lack of sporting pretensions. Compared to the 2.2-liter models, the 2.5-liter offered a noticeable performance improvement. Compared to the 2.8-liter, it was less powerful but more fuel-efficient. In terms of reliability, the Commodore B was generally considered a dependable car, although maintenance could be relatively involved due to its older technology.
Legacy
The Opel Commodore B 2.5, while not a particularly rare or highly sought-after classic today, holds a place in automotive history as a representative of 1970s European motoring. The 25S engine proved to be a reasonably durable unit, and many examples are still on the road today. However, finding parts can be challenging, and maintenance requires a degree of mechanical expertise. In the used car market, the Commodore B 2.5 is often appreciated by enthusiasts for its classic styling, comfortable ride, and relatively simple mechanicals. It represents a bygone era of automotive design and engineering, offering a unique driving experience that is increasingly difficult to find in modern cars.
