Here are the differences between diesel and gasoline engines:

1. The first main difference is the fuel used and it could not be interchanged.
2. Next is, Gasoline engines have spark combustion while Diesel engines have compression combustion. This means the Diesel engine has no ignition system like ignition coil or electronic ignition, breaker point, spark plug and high tension wires.
3. Another is Diesel engines have a higher compression ratio compared to Gasoline engines (e.g. Diesel compression is usually around 23 is to 1, while Gasoline compression is only somewhere 10 is to 1). This means the larger number of fuel and air mixture is compressed only to 1. An exception here is the Volkswagen Golf Diesel engine of only 1.5 liter based on a gasoline engine.
4. Diesel is injected directly into the combustion chamber while Gasoline is either through carburetor or injection outside of the combustion chamber.
5. Diesel engines will need more frequent and regular change of filters because it requires a “cleaner operating environment” compared to a Gasoline engine.
6. Lesser parts to be maintained in a Diesel engine as against a Gasoline engine.
7. Diesel engines are usually larger and heavier compared to Gasoline engines due to its larger compression ratio and strokes needed.
8. Diesel engines operate at higher temperatures as an aid to compression combustion.
9. Diesel injection requires higher pressure to atomize the fuel compared to the EFI of gasoline engines.
10. Pistons, connecting rods and crankshafts of Diesel engines are more robustly constructed compared to gasoline engines.
11. Some Diesel engines do not have partial vacuum for the inlet manifold requiring it to have a separate vacuum pump for power servo brakes. (Check your diesel engines for this)
12. Diesel engines can be “crank-started” without a battery because it does not require spark from electric current. Gasoline engines always need a good battery for a good spark to do a “crank-start”.
13. Some Diesel engines have heater plugs as an aid to cold starting. Cold cylinders reduce compression making starting difficult.
14. Diesel engines require periodic injector service at about 50,000 mile intervals.
15. On the average, Diesel engines are noisier and have more vibration compared to Gasoline engines. This is more evident when diesel engines have aged.

Though this may not have to do much on engine operation, Diesel engine vehicles have sturdier suspension and engine support compared to Gasoline engine. For suspension, it is to offset the heavier weight of the engine. For engine support, diesel engines vibrate more due to higher compression ratio and longer strokes.

Also, it is a better practice to have regular oil changes with Diesel engines because the engine needs to work harder with long strokes. This goes with a less clean operation and combustion of diesel compared to gasoline.