Diesel engines have pistons that look different from the ones you’d see with a gas engine. There’s a reason why that’s the case, and it’s all about performance.
Gasoline and diesel engines feature many differences aside from fuel type. Compared to gasoline engines, a diesel is typically a lower-revving, torquier design, hence why it’s often preferred over gasoline in many industrial and heavy-duty marine applications. They also have some differences in maintenance procedures, they produce a very characteristic sound (with some sounding truly incredible), and they’re typically more fuel-efficient. This is because of how a diesel engine works: namely, instead of using a spark plug, a diesel engine ignites through sheer compressive force. Basically, a diesel engine compresses the air inside of the combustion chamber so much that, when fuel is injected, it essentially spontaneously ignites. This is why diesels don’t need spark plugs, for instance. But it also means that mixing the fuel and air can be tricky, which is why diesel engines have specially-shaped pistons.
A diesel engine’s piston head looks like someone took a scoop out of the top.
