Basically the same design but the M104 has some head improvements. In high mile threads there are cars that hit 400k. From what I've read you expect 250k with proper maintenance before you need head gasket and or valve work. Along the way you may need transmission, water pumps, alt regulators, relays, bushings, etc. Some believe the bottom end should last indefinitely...

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'88 300TE, 175k, black RENNTech 3.6L Recaro C's AMG 1 SOLD
'92 500E, 110k, Spruce green, stock SOLD
'94 E320 Cabriolet, 130k, E500 wheels, Emerald green SOLD
'94 E320 Cabriolet, 110k, black, stock, SOLD
'88 300TE, 229k, dark grey, SOLD
'90 300CE, 212k, white, new paint, SOLD
'91 300E, 209k, white, rebuilt head SOLD
'74 914-6, grey, 2.7L 325hp twin turbo Audi conversion