Rick. "In 1987 they came out with the 300SDL, which was a 3.0 straight six engine. This engine proved to not be a durable as the 617series of 5 cyl. turbo diesel engines."
Wait just a minute here! The SDL is a terrific car! First of all the SDL first came out on the market in 1986 not 87'. As a 1986 SDL owner myself, I can assure this car is VERY reliable and durable. What they are referencing here sel is the fact that the SDL has the aluminum head. Big deal guys! Most cars today have aluminum heads and there are several posts on this forum involving cars with IRON heads that have cracked because of overheating as well. I chose the SDL because of the following benefits:
#1 Very roomy, very large, extended wheelbase with sinful amounts of interior room, thus the "L" added to SD..
#2 Much much better built than the 350. The general consensus is stay away from the 350, NOT the 300SDL.
#3 Still gets great gas mileage, mine goes over 580-600 miles per tank usually.
#4 The 300SDL sdl is one of the quickest and highest top speed diesels every made.
#5 Unlike the SD, you don't have the pain of manual adjusting valves every 15k miles.
Bottom line, these benefits clearly outweigh the "downside (if it even is one) of having an aluminum head and you don't have to adjust the valves.
"I would not rule out the '86-87 300SDL. I ALMOST bought one 3 years ago (and sometimes still kick myself that I didn't!) 400 E is right, sd's are great and so is the 400E but the SDL (in my opinion) is a better car than the SD for the above reasons. The 400E is a different animal but great car. (END SOAPBOX)