To truly bring the fight to the BMW 5-Series and Mercedes-Benz E-Class, the 2013 Lexus GS will have to deliver on performance, style, comfort, and, for many, efficiency. In Europe, at least, that means an available four-cylinder diesel. According to the latest reports, Lexus is planning to do just that.

We here in the U.S. won't likely see such a small diesel in the GS, however, with a V-6/hybrid combo, or even a V-8/hybrid as seen in the LS hybrid, far more likely. For Europe, however, diesel engines have much broader acceptance than gasoline hybrids, and according to Autocar, the company is planning a version of the GS with a new small four-cylinder diesel, possibly a revamped version of the 2.2-liter unit used in the U.K., offering about 150 horsepower.

Due to arrive in Europe in 2013, if it does indeed arrive, the diesel would put the BMW 520d on notice, or at least offer some alternatives to efficiency-minded luxury buyers on the continent.

We won't have too long to wait to find out, however, with the official unveiling of the new GS 350 coming at Pebble Beach in just a few weeks, and more information to follow in September at the Frankfurt Auto Show. MotorAuthority will be live at both to bring you the latest news and live photos as they happen.