Diesel Engines and Fuel economy

Diesel-engined versions tend to show better fuel economy figures than gasoline-burning versions - checking a few offical figures shows that a small diesel 4x4 has better touring economy than the supercharged Mini Cooper S or many large saloon cars.

Note though that gasoline contains about 15% less energy than diesel fuel per unit of volume, so direct comparison of fuel economy numbers can be misleading. Also, bear in mind that diesel is a more polluting fuel than gasoline, so a direct comparison of gallons/liters per mile/kilometer can be misleading.

Although SUV's have the image of being fuel hogs, compared to sport editions of standard cars, luxury cars and mini vans the SUV's don't come out so bad. Luxury cars and mini vans can have the same or even more weight than a SUV. Standard cars with a diesel engine can weigh more than a regular SUV. Sport editions of cars and tuned cars can have really bad fuel economics. Luxury cars and limousines often have larger engines than SUV's.

The smallest consumer gasoline cars average from 1 liter per 16KM up to 1 liter per 20KM (±40-50 mpg). Average gasoline cars average from 1L / 8KM up to 1L /15KM (±20-35 mpg). Most gasoline luxury cars, limousines, SUV's, sport editions and tuned cars vary from 1L / 6KM to 1L / 12KM (±15-30 mpg).

Ok, it's been established that diesel engines are powerful and more economical. Deisel is also cheaper compared to gas. So what stops manufacturers from churning out diesel SUVs and 4X4s?