BMW 315: Which Version to Buy and Why
The BMW 315 catalogue contains two versions, both named 1.5 MT, so power is the essential identifier: one produces 40 hp (30 kW) at 4,300 rpm, while the other produces 34 hp (25 kW) at 4,000 rpm. Both belong to the sole generation, a Roadster produced from April 1934 through December 1937, and both use a 1,490 cc Gasoline engine, 4-speed Manual gearbox, and RWD.
The BMW 315 catalogue contains two versions, both named 1.5 MT, so power is the essential identifier: one produces 40 hp (30 kW) at 4,300 rpm, while the other produces 34 hp (25 kW) at 4,000 rpm. Both belong to the sole generation, a Roadster produced from April 1934 through December 1937, and both use a 1,490 cc Gasoline engine, 4-speed Manual gearbox, and RWD. Because their fundamental layouts are identical, the choice comes down mainly to output, compression ratio, and fuel-tank capacity. On the available specifications, the 40 hp 1.5 MT is the stronger all-round choice; the 34 hp 1.5 MT is the alternative when the lower-output specification itself is preferred.
BMW 315 generations and version choice
The BMW 315 has 1 generation in the catalogue. It ran from April 1934 to December 1937, used the Roadster body style, and included 2 versions. There is therefore no later generation to compare with the first one, and the data records no restyling or generation-to-generation mechanical change. Buyers comparing BMW 315 versions are choosing between two specifications within the same generation rather than between different body styles or production eras.
Both versions carry exactly the same catalogue name, 1.5 MT, and both have version dates running from January 1934 through December 1937. To avoid confusing them, they should be identified as the 1.5 MT with 40 hp and the 1.5 MT with 34 hp.
BMW 315 engine and specs comparison
The two BMW 315 engines share nearly every recorded core specification. Each displaces 1,490 cc, uses Gasoline, and has 6 cylinders in an Inline layout. Each cylinder has 2 valves, boost is No, and the fuel system is Carburetor. Both engines have a bore and stroke of 58 × 94. Engine position and fuel grade are not measured for either version.
The differences are concentrated in output and compression. The 40 hp 1.5 MT develops 30 kW at 4,300 rpm and has a 6.8 compression ratio. The 34 hp 1.5 MT develops 25 kW at 4,000 rpm and has a 5.6 compression ratio. The stronger version therefore provides 6 hp and 5 kW more, reaches its stated power at an engine speed 300 rpm higher, and has a compression ratio higher by 1.2.
| Version | Power | Torque | Displacement | Fuel | Cylinders | Layout | Boost | Gearbox | Drive |
|---|---|---|---|---|---|---|---|---|---|
| 1.5 MT (40 hp) | 40 hp / 30 kW at 4,300 rpm | not measured | 1,490 cc | Gasoline | 6 | Inline | No | 4-speed Manual | RWD |
| 1.5 MT (34 hp) | 34 hp / 25 kW at 4,000 rpm | not measured | 1,490 cc | Gasoline | 6 | Inline | No | 4-speed Manual | RWD |
Using the common 1.49-litre displacement, the 40 hp 1.5 MT produces about 26.8 hp per litre, while the 34 hp 1.5 MT produces about 22.8 hp per litre. That gives the stronger version an advantage of roughly 4.0 hp per litre. In relative terms, its 6 hp lead represents about 17.6% more power than the 34 hp version. Its 30 kW output is 20% greater than the other version’s 25 kW.
Both BMW 315 versions send their output through a 4-speed Manual gearbox to RWD. The catalogue provides no alternative transmission or drive system, so these features do not distinguish one version from the other.
BMW 315 performance, mpg, and economy
Acceleration from 0–100 km/h is not measured for the 40 hp 1.5 MT and not measured for the 34 hp 1.5 MT. Top speed is also not measured for both versions. Consequently, the extra 6 hp supports a clear output comparison, but it cannot be converted into a catalogue-backed claim about acceleration or maximum speed.
City fuel consumption is not measured for either BMW 315 version. Highway fuel consumption is not measured, and combined fuel consumption is not measured as well. CO₂ output and environmental class are also not measured for both versions. There is therefore no measured mpg or consumption figure with which to declare either engine more economical.
The fuel tanks do differ. The 40 hp 1.5 MT has a 50-litre tank, whereas the 34 hp 1.5 MT has a 35-litre tank. The more powerful version carries 15 litres more fuel capacity, an increase of about 42.9% over the smaller tank. This indicates greater fuel capacity, but range cannot be calculated because consumption is not measured.
BMW 315 dimensions, weight, and chassis specs
Kerb weight is not measured for either 1.5 MT, and gross weight is likewise not measured. Because no weight is supplied, weight per horsepower cannot be calculated for either version. Ground clearance and wheel sizes are also not measured for both BMW 315 specifications.
The recorded chassis equipment is identical. The 40 hp 1.5 MT and 34 hp 1.5 MT both use Dependent, leaf spring front suspension and Dependent, leaf spring rear suspension. Both have Drum front brakes and Drum rear brakes. None of these specifications provides a reason to select one version over the other.
| Version | Kerb weight | Gross weight | Ground clearance | Tank | Wheel sizes |
|---|---|---|---|---|---|
| 1.5 MT (40 hp) | not measured | not measured | not measured | 50 litres | not measured |
| 1.5 MT (34 hp) | not measured | not measured | not measured | 35 litres | not measured |
BMW 315 problems and reliability data
Problems and reliability are not measured for the 40 hp 1.5 MT and not measured for the 34 hp 1.5 MT. The supplied data contains no failure rates, service intervals, repair records, or durability measurements. Neither version can therefore be recommended on reliability grounds from these specifications alone.
The same limitation applies to purchase cost. Price and sale information are not available, so the data cannot show what extra money, if any, the 40 hp version requires. It can show only what its different specification provides: 6 hp more power, 5 kW more output, a compression ratio higher by 1.2, and 15 litres more tank capacity.
Which BMW 315 1.5 MT should you buy?
Choose the 1.5 MT with 40 hp if the priority is the strongest recorded specification. It delivers 40 hp instead of 34 hp, 30 kW instead of 25 kW, and approximately 26.8 hp per litre instead of 22.8 hp per litre. Its 50-litre tank also exceeds the other version’s 35-litre capacity by 15 litres. Since gearbox, drive, engine displacement, cylinder arrangement, valve count, fuel system, suspension, and brakes are the same, these gains do not require accepting a different recorded drivetrain or chassis layout.
Choose the 1.5 MT with 34 hp only if that lower-output specification is the intended target. It retains the shared 1,490 cc Gasoline, 6-cylinder Inline, naturally aspirated configuration with boost listed as No, plus the same 4-speed Manual gearbox and RWD. Its distinguishing figures are 34 hp, 25 kW at 4,000 rpm, a 5.6 compression ratio, and a 35-litre tank.
Overall, the 40 hp 1.5 MT is the better specifications-based buy. The 34 hp 1.5 MT offers no recorded advantage in fuel consumption, performance, weight, dimensions, reliability, transmission, suspension, or braking because those measures are either identical or not measured. Without price data, the extra cost cannot be judged; without economy and performance measurements, operating savings and speed differences cannot be claimed. Based strictly on the available numbers, however, the 40 hp 1.5 MT provides more power per litre and greater fuel capacity while preserving the same recorded mechanical format.