Who makes the 3. L diesel engine?

Who makes the 3. L diesel engine?

GM Duramax 3. Liter I-6 LM2 Turbo Diesel Engine. The 3. L Duramax diesel is designed for superior fuel economy. It achieves up to 23 MPG city and 29 MPG highway, providing significant savings for daily drivers and long-distance commuters alike. The 6. L gas engine, while powerful, delivers lower fuel economy, generally around 17 MPG city and 23 MPG highway.