However, BMW is looking at adding four cylinder engines just as it does in the regular 5-series. First out of the gate could be the 2.0-liter twin turbo four cylinder diesel and the single turbo 175 hp could appear as well. In the manual transmission 320d with the 175 hp engine, the EU test cycle is completed at 49 mpg (U.S.). The bigger and heavier 5GT would likely get closer to 40 mpg, still an admirable number for such a large car. Even the current 530d GT is rated at 36.2 mpg (U.S.). Unfortunately, we likely won't get any of these engines anytime soon.