A C240 is a C Class chassis W202 and W203 which runs from 1996 to about 2007. The C240 has a 2.6 litre V6 in all the years. Minor tweaking and upgrades are on the newer ones but it is essentially the same basic engine. The badge name C240 is absent on the W204. Think the new engine is a 2.5 V6.
An E240 is an E Class that ran the model versions W210 and W211. It also had the same 2.6 litre V6 based on the M112 block.
Note too that these engines are twin spark and make surprisingly admirable torque for the size. Two spark plugs help level out the efficiency.
One of my favourite V6 engines.