The GL450 gets a gasoline-powered 4.7-liter V8 good for 335 hp and 339 lb-ft of torque. In Edmunds performance testing, the GL450 went from zero to 60 mph in 6.7 seconds. Fuel economy suffers, however, with an EPA-estimated 13/18/15. The GL550 gets a 5.5-liter V8 good for 382 hp and 391 lb-ft of torque |