BMW M52
The BMW M52 is a straight-6 DOHC piston engine which replaced the M50 and was produced from 1994-2001.
Compared with its M50 predecessor, the M52 uses an aluminium block (except for North American models, which retained the iron block). In 1999, the M52TU ("technical update") was released, upgrading the variable valve timing to a system with continuous control for both inlet and exhaust camshafts (called "dual VANOS" by BMW).
The M52 and S52 engine was on the Ward's 10 Best Engines list from 1997 to 2000.
The S52 engine used in the North American M3 engine from 1996-1999 is based on the M52 engine (in other markets, the equivalent engine was a 3.2 litre version of the S50).
Read more about BMW M52: Nikasil Problems With High Sulfur Fuels, Models