The GL-class is roomy, comfortable and handles well for a big SUV. The diesel version feels sluggish off the line, but pulls strongly once under way. Fuel economy is significantly better than the gasoline-powered GL450 V8 we tested in 2006. Our diesel version's 20-inch run-flat tires reduced the steering feel and compromised ride comfort. Overall, the GL diesel is a smooth, luxurious coach, but the GL450 delivered a more pleasant driving experience A substantially redesigned model debuted for 2013.