Features: 4-speed AT, RWD, PS, A/C (worked occasionally), cruise control (worked on rare occasions), seats 5
Purchased for/from: $2,500, including help with veggie-oil conversion. Purchased from a 30-something hippie from California.
Summary: I absolutely loved this car. The engine was converted to run on vegetable oil. I collected waste vegetable oil from two Chinese restaurants, filtered it in the garage, and ran the car on it. During the summer I could run the car on 100% vegetable oil (I never did though, I always added at least 10% diesel to the fuel tank to prevent the vegetable oil from coking [ie forming a sticky sludge] on the injectors), during the winter I would blend in about 10% kerosene and 5% diesel (this thinned the oil so that it would continue to run smoothly even in colder temperatures). The acceleration on this car was pretty slow, as it has a very heavy body and an automatic transmission. However, once the car got going it had no lack of power, easily climbing hills and cruising the freeway at 75+ mph (I won't say the fastest I ever drove that car, but suffice it to say it was well over 75 mph).
I did a ton of work on this car, and learned most of what I know about cars and diesel engines from owning it. Among the things I did to it: installed a higher-output alternator, installed new brake pads, installed a flat-plate-heat-exchanger, fixed vacuum system leaks, replaced the oil pan gasket, adjusted the idle, and replaced the valve cover gasket. For regular maintenance, I adjusted the valve lifter clearance, changed the oil and oil filter, rotated the tires, and replaced fuel filters.
My vegetable oil conversion on the car consisted of: fuel-line heaters, injector heaters, a 30-plate flat-plate heat exchanger, an auxiliary inline fuel pump, an auxiliary inline fuel filter, and a switch in the dashboard to turn the heaters on (this on/off switch option was so the car could continue to run on regular diesel fuel as well). My vegetable oil filtering setup consisted of: 55-gallon-drum holding tank and gravity filter which filtered first through old sewn-closed jean legs and then through 1-micron bag filters, a rotary barrel pump, and a Goldenrod inline fuel filter on the hose that went to the car for filling up the fuel tank.
What I Liked: The most comfortable car I've ever driven, decent (for its weight) fuel economy (22-28 mpg, although this wasn't a huge factor since I was running on free fuel), great power on the freeway, roomy trunk and interior, driving a car that was $30,000 when it was new in 1979. Truly, a "luxury car" in every sense (except in the sense that some of the features it had didn't always work). Also, handled decently in snow despite being RWD, probably because it was so heavy.
What I Didn't Like: Having to buy expensive Mercedes parts, having to fix something on the car about once every 3 months, slow acceleration. Most hated of all: my jury-rigged speedometer that I installed after the original speedometer broke. At Pick-n-Pull, I pulled the speedometer from a gasoline Mercedes of the same era. It "worked" in my car except that it had to be installed sideways and I had to mentally convert the speeds it showed to actual speeds (so, for instance, when the speedo said "25 mph" I was actually going 35 mph, and when it showed "50 mph" I was actually going 65 mph). Then, to top it all off, the dash (from the area of the speedometer) started buzzing every now and then, LOUDLY (sounded like a swarm of bees in my instrument panel). I had this problem with both the old and the new speedometers. It would usually crop up just once in a while and then go away, but by the time I sold the car there was always about a 50/50 chance that the dash would be buzzing.
What Happened to It: I sold it for $900 to a guy from Seattle, and made a huge mistake: I didn't take off my Nevada license plates (the tabs were still good for about 8 more months). Then, like the piece-of-shite jerk that he was, the buyer racked up numerous parking and light-camera tickets, never responded to ANY of my dozens of emails and calls, and basically left ME to deal with the Seattle Municipal Court to explain that I no longer owned the car and had NOT acquired those tickets of my own merit. The thing that finally seemed to do the trick (ie got the court to stop hounding me) was explaining (with the Bill of Sale and the threat of corroborating witnesses) that not only did I not get those tickets myself, but also that I couldn't possibly have based on the times and places the tickets were acquired. It turns out it is physically impossible to be sitting in a class in Ellensburg, WA, while simultaneously illegally parking a car in Seattle, WA.