Your W210 has an inline pump instead of a common rail.... no?

2- tank systems are great if you switch over once a day and then drive for long distances. They are are not-so-great if you make a lot of stops.

Multiple purge cycles, as in daily stop/start errand running, end up transfering much of your petro diesel over to the WVO tank. The perverse side-effect of this is getting to watch your petro diesel tank level drop while the WVO tank level actually increases

I understand GreasedLightning's frustration with this - thus wanting to leave the vehicle idling instead of purging.

Single tank must include enough heat so the injected fuel atomizes the same way standard petro diesel does. That has been determined scientifically to be around 250 degrees F. Many are satisfied to run WVO at their coolant temperature of about 170 degrees F since the energy to do that is free (not including the cost of heat exchanger, plumbing, etc). Blending WVO with petro wihout heating is something you can do for a while, but over time the injectors with coke up - causing hard starting, smoky exhaust, etc. Also, your steel tank, with the help of oxygen will automatically start polymerizing any WVO in the blend. This will cause a light brownish coating to deposit on the walls of the tank. Over time, this coating gets thick enough to come off in little bits... eventually in big chunks which will plug up your fuel filter - and will require tank removal and detergent/steam cleaning to fix the problem. It will also cause your fuel level sender to stop working.

If you are going to do this, heat the fuel (electric line heaters are cheap and work great) - and in a few years get a backup spare tank, and keep some spare fuel filters in the trunk .