One of the primary considerations when choosing an engine is fuel consumption. Different engines manufactured by different companies all consume fuel at different rates. However, when you add power, climate, metering methods and technology, maintenance, and other factors into the equation, the answer might not seem so straight forward.
Brake Specific Fuel Consumption (BSFC) is the best way to determine fuel consumption between engines. It is the ratio of fuel consumed to power produced.
For example, on the MarineDiesel VGT500, at full load, 3,600 RPM, the engine consumes 230 g/kWh of diesel. However, at different loads and different RPM levels, the engine will consume a different amount of fuel. That is why when you see BSFC numbers, the engine speed is always listed, and it is important to look at the fuel consumption curve provided by the manufacturer (if they do so).
When things get complicated is that, though BFSC, g/kWh is generally the standard, often engine makers will show fuel consumption in imperial units, or as simply a flow rate, as in l/h or gal/h. This does not take into account the engine power, but merely a rate based upon time. In order to truly compare engines and performance, the BSFC is a must.
Generally, fuel consumption rates for marine engines in the same class as the VGT series will show BSFC rangine from 200 to 240 g/kWh, depending on the maker. Gasoline powered engines typically have far higher consumption rates than diesel engines.
It is also important to recognize that fuel consumption is greatly impacted by maintenance (or lack thereof), climate, operating conditions, fuel quality, and engine compression (set by the ECU). Maintaining the engine according to the manufacturer’s recommendations and oprating within the designed parameters can greatly reduce fuel consumption over the long term.