Originally Posted by Zacharias

Short answer: this had better be CHEAP. It may be a paperweight. Plus I believe an '81 will have the Type II ACC (servo, etc.). If you don' t know about that system, then read up on it before you dive in.

Longer answer: you need to find out how long the PO ran veg, what exactly is meant here by veg (veg oil off the shelf, or waste oil, and if the latter - was it properly filtered and cleaned).

Also, was any actual veg setup (heat) on the car? From the sounds of it, I suspect it was just another bonehead dumping veg into the tank.

If it was fresh veg oil, and it wasn't for too long, you may be able to fix things with a good cleaning and flushing. If it was used veg dumped in with no heat and possibly no proper cleaning... you don't need this adventure.

Google ring polyermization if you want an idea of what dirty and/or unheated veg will do to a motor. Mercedes are often victims as people get away with it longer (the motor still runs) than would be the case with, say, a VW diesel.