How much fuel do various types of engines burn per power output? I'm especially interested in naturally aspirated piston engines, and comparing two-stroke to four-stroke.
The wikipedia article gives the value for several specific engines, but they're mostly for either aircraft or marine applications.
This webpage provides a very concise comparison for several different engines:
+------------------------------------------+----------+----------------+-----------+
| Engine | @ 1K RPM | @ Peak Torque | @ Peak HP |
+------------------------------------------+----------+----------------+-----------+
| 4-stroke (low compression, carburetor) | 0.62 | 0.47 | 0.52 |
| 4-stroke (high compression, carburetor) | 0.60 | 0.42 | 0.47 |
| 4-stroke (high compression, closed loop) | 0.52 | 0.35 | 0.42 |
| 4-stroke (supercharged, carburetor) | 0.75 | 0.50 | 0.55 |
| 4-stroke (turbocharged, closed loop) | 0.57 | 0.45 | 0.50 |
| 2-stroke (low compression, carburetor) | 0.85 | 0.55 | 0.60 |
| 2-stroke (high compression, carburetor) | 0.80 | 0.50 | 0.55 |
| Diesel 4-stroke | 0.35 | 0.25 | 0.30 |
| Diesel 2-stroke | 0.40 | 0.29 | 0.34 |
+------------------------------------------+----------+----------------+-----------+
4-strokes are more BSFC-efficient than 2-strokes
best BSFC occurs at peak torque
Because that's where the engine is most efficient
less diesel needed per unit work compared to gasoline
Now you know why diesels are the go-to choice for heavy trucks.
¹ - Alternatively, BSFC = fuel flow rate per unit power
