1981 300sd

[1stimer]

Well I have been reading the posts for quite a while now, and I think I have decided on an early eighties diesel. I have always admired mercedes, but know nothing about diesel engines. I looked at a 1984 300td yesterday which was junk. It needed way too much work than I am willing to put into it. Next week I am going to look at a 1981 300sd. 140k miles. Owner is 2nd owner who bought 3 years ago for 7k in his words to prepare for y2k. He had a line on some bio-diesel fuel from Maui, and was preparing for a lack of diesel fuel. He said he bought a couple of barrels of this stuff made from used cooking oil. He says the ac has just gone out, but other than that the car needs nothing. He is selling because he does not need the car anymore. He also has stated car gets 30 mpg. He is asking 2900/obo. What is the most important and costly things to look for? Did he damage the engine from using this fuel? How could I tell? My diy talents have thus far been limited to routine maintenece. brakes, filters, oil changes. Well, I will let you all know how the diesel market is over here in Hawaii, and thanks for all the information in the posts I have and will continue to read. Aloha