One real benefit from the 722.6 box is the overdrive fifth gear.
With the steeper 3.27 (instead of 3.07 on the C280) final drive ratio, the C230 spins:
195/65-15" tire is 75.8" in circumference. It spins 807 times per mile. (we'll go imperial) With the tire spinning 807 times per mile, then the drive shaft is spinning 807*3.27 = 2638 revs per mile, or revs/minute at 60 mph.
Well, not bad. But, the 722.6 has a .83 overdrive ratio for it's fifth "cog."
So, 60 mph is only 2189, or 2200 rpm. My tach seems to read about 2300, maybe 2400, but I know it's a little high, based on using the PBU diagnostics mode.
2200 rpm is a nice relaxed rate. The 190E 2.6 of ours spins much faster (like 3000) and therefore burns more fuel and causes more wear. Finding a five speed manual car in the W201 or W124 chassis is nice...
1998 C230 "Black Betty"