So anyone who has seen many of my "learn me" threads might know that I like to go fast (you might also assume this by my membership on this site).
My history with diesels:
I've owned two diesels, a 1980 Mercedes 300TD wagon with the NA straight 5 automatic and an 82 240d Sedan with a 4 speed. Both were painfully, aggravatingly slow. The 80 had 80 hp and the 82 had 60 (when they were new). The wagon was an absolute dog, would never downshift, and got about 25 mpg (28ish on flat land). The 240 got better mpgz and was pretty peppy with the 4 speed, but still didn't have enough balls to change lanes in traffic. I hated/loved both cars. They were rock of ages reliable, but I spent a lot of time yelling at them to accelerate. At some points I decided that I'd rather have a gasser to satisfy my heavy foot (or it might have been because both Mercs were rusting apart, I can't remember).
That brings us to today.
I paid $3.64/g for gas today and was furious (I hadn't got gas in 2 weeks and last time it was $3.45ish/g). I glanced at the big sign, diesel was still under $4/g ($3.95 iirc, so local biodiesel should be ~$3.85/g). I haven't paid any attention to the price of diesel since I sold my last one. I was a bit jaw dropped, since I figured the price of gas and diesel would rise at about the same rate. Last time I had a diesel, the price of gas was just over $3 and the price of diesel was a little over $4. It didn't seem as worth it then, but it's starting to look more and more worth it now.
So I'm considering buying another diesel. My only problem is I don't really know how to fix/diagnose a diesel, niether of my Mercs ever had any real problems. I also don't really know what makes a good or bad diesel. I really liked the Mercedes engines, but have heard very bad things about American coal rollin' power plants (at least the ones from the 80's that I can afford). What I've heard about VW's, Audis, Volvos, Isuzus, Fords/Mazdas have all been mixed reviews. I might be looking for something other than a Merc since their prices have shot up with the local biodiesel/kale chips/chia seed/quinoa/can I bum some weed/hipster fad.
Another thought: Do y'all think the price of gas will soon exceed the price of diesel, and do you think that will change drooling-cheeseburger face stuffing-no turn signal using-breathing on the back of your neck in line at the bank-oops I didn't use birth control-Americans to drive something other than giant pig-wagons?
Since this is such a wall of text, here's some pictures of rusty Mercedes.
If you compare cost of fuel, diesel wins hands down, massively, everytime. In trucks, diesel MPG can almost be double of its gas counterpart, but fuel is only about 20% more.
Right now Ford Focus is bragging about MPG that is twice the average car... which is something like 27mpg. Compare that with the new Chevy Cruze or darn near any TDI that is getting 50+ and its a no-brainer.
Diesel technology has come a long way also. Diesels are quite quick, sometimes faster than their gas siblings.
Now, if you're talking about fixing up an old Merc diesel... you may want to invest in some upgrades; turbo, injectors, fuel pump... its pretty easy to get 150-200 hp out of them. Not cheap, but easy.
Oh... and as far as diagnosing or fixing a diesel? Take all you know about gas engines and make it easier. No ignition system, no throttle. Its a fuel pump and an air pump. Mix em together and go zoom.
If you take away the "unknown" factor, diesel is super easy. I know its not something you know a lot about, but once you learn how to fix the very few things that could go wrong, its just like working on a gas engine. Its just that the fuel smells different.
In reply to curtis73:
I'd be looking at something from the 80s. No computer. I know of Black Smoke Racing, and those Scandinavian recknecks are bad asses. But stock sounds like more money in my pocket, which is something there is less and less of these days.
New question after looking at Craigslist: Why can't anyone spell diesel?
Having said that, I wouldn't own a VAG TDI if you paid me. I would own another W210 Merc. I had a 99 E300TD. 170 hp, 34 mpg, super luxo ride, and it was super reliable for me up until the day I sold it with 247k on it.
Another thing to mention... many of the things you do to a diesel to get more power actually increase the MPG. Its a long story, but even adding more fuel can help MPG because of hotter combustion and more efficient burning. Advancing the injector timing can have very big benefits with MPGs as well. As with any engine, the manufacturer makes it with emissions and NVH in mind, not peak performance.
Let me know when you find out why nobody can speel Diesel.
You may also want to look for 300D Turbodiesels and maybe even a 300SD. That said, for 80s high mileage, go look for a Rabbit Diesel.
Well, there is good and bad news there. Early diesels tend to suck. Low injection pressures, indirect injection, little or no turbos... they tend to be slow. Ever drive a diesel Rabbit? 0-60 in three months.
So I think you'll end up with a bit out of pocket for upgrades to get enough oomph to make you happy.
The 170hp in my W210 was done with the 3.0L I-6 that is the same basic architecture as the earlier OM6 engines. Maybe find an 80s I-6 turbo to start with. I think they were 120hp to start with, so 150-175 should be super easy.
I before E except after C. I'm not sure why many people don't remember that rhyme. 
The cost of fuel wasn't in your favor when you had the old Mercs because the car(s) you replaced them with probably got a little better gas mileage with cheaper fuel. I would say that you have to go after a 00s Jetta or Passat TDI. Those get about 45 mpg and are reliable. I know because my dad had one and nobody wanted to sell me one for a good price last year.
I'm also hearing that the newest diesels aren't as fuel efficient because of a different fuel injection system.
Just had a thought: 240d + autox = lolwut?
I am waiting for the BMW diesels to drop in price while contemplating doing a diesel swap in my Xterra.
Diesel sucks in anything but trucks. 
They don't rev and they sound like E36 M3.
or seize, weird, vein, their, foreign, feisty
and a 160+ more
http://en.wiktionary.org/wiki/Category:English_words_not_following_the_I_before_E_except_after_C_rule
In reply to 93EXCivic:
This is why I liked the 240d. It was the only diesel I've seen that you could (relatively) rev to the moon. Peak power was at like 4200. I think I remember the manual listing different rev limits for hills, flat land, and down hill. Around 3500 it sounded like it was going to explode. I was wrong about the hp rating, that thing made a knee-shaking 72 horses.
It's basically a 22R.
I loved my '84 300SD. But it never got the mileage I'd hoped it would, and it was a rough drivetrain on the highway. I don't know why I loved it....
IMHO, go with a modern diesel or don't go diesel at all. Old diesels are slow and rough.
The fuel cost seems to be pretty much a wash. MPG/cost.
It is the buy out and maintenance that seem to be the deal breaker.
OH, we can't forget the UREA(sp). An added cost on the new ones.
skierd
Dork
4/11/14 12:42 p.m.
If it's a newer, at least late 90's turbo diesel i.e. a VW TDi, I'd say you're on the right track.
But an obscure-ish 80's Euro diesel that no one outside of GRM land remembers or wants to remember that barely gets better mileage than their contemporary gas counterparts (or newer, cheaper gas cars before the Great Bloating of MY200X) while being noisier and smellier? Unless you're making your own diesel, I'd pass...
iceracer wrote:
OH, we can't forget the UREA(sp). An added cost on the new ones.
But you get what 1500 miles to 5gal of DEF@ $3-6/gal?
More like 10,000 miles on a gallon or two. The cost of Urea isn't a big deal at all, IMHO.
RoughandReady wrote:
What is urea?
Diesel exhaust fluid. Or the newest crap to make us feel good about the environment by putting more crap into it.
DrBoost
PowerDork
4/11/14 5:05 p.m.
Urea is whizz that goes in a second tank to spray in as an after-treatment to clean up emissions. That's an over simplification that some will jump on me for, that's fine.
I had a 1992 300D. It was fine in the accel department. I sold it with 310,000 miles. It was reliable, but it needed lots of things that I didn't do to it, like 438 suspension bushings. I got about 30 mpg in mostly highway driving. parts weren't terrible, except internal engine stuff. The oil pump, all-in, was $500!!! That's be doing the labor and only charging myself a candy bar. It blew my mind with how well it drove and shifted. But the vacuum system will make you cry three times per year.
Now I'm driving a 99 Golf TDI. It's 100X better on accel than the Merc. I also get 50+ mpg on the same commute. I searched long and hard to find one with manual windows, HVAC, Trans, basically I wanted as few wires as possible.
The worst thing about the TDI? The interior plastics are made out of compressed graham cracker crumbs with a little baby spit as a binding agent.
