Mainly divided into gasoline and diesel pistons
Gasoline engine and diesel engine piston both in the main structure is very different, usually gasoline engine piston diameter is relatively small, wall thickness is relatively small, the weight is relatively light. While the diesel engine piston diameter is larger, wall thickness is thicker, heavier weight. The shape of the piston is quite different.
The biggest difference between gasoline and diesel engines is the ignition method and air intake: gasoline engine into the cylinder is a mixture of oil and gas combustible gas, diesel engine is pure air; gasoline engine is ignited by the spark plug, diesel engine is compressed air to reach the diesel auto-ignition temperature from the injector holes will be sprayed into the diesel fuel, due to the high temperature of this time, diesel fuel auto-ignition.
To say the difference, the most likely is in the skirt of the piston, because most diesel engines have a longer piston stroke than gasoline engines, and may have a special shape in the skirt to match the movement of the flywheel, but not all diesel engines are like this.
Take the pistons of a 2-valve gasoline engine and a diesel engine and compare them: the difference is in the top of the piston. Gasoline pistons are flat, diesel pistons have combustion chambers at the top. This is the biggest difference. Then take the multi-valve gasoline engine piston and diesel engine piston comparison: the top of the combustion chamber. But the gasoline engine is simpler. The distance between the piston ring grooves is larger in the diesel than in the gasoline engine. The oil ring grooves of the diesel have holes. Gasoline engines do not. All in all there is a big difference.