[E300D]

The reason these Mercedes diesels retain their value is that they run forever, get 25/35 mpg and they look nice at any age as long as the paint is shiny and the rims are not pealing.

The Quality of build on these mid-90s diesel Mercedes is much higher than more recent MB vehicles and there is also an Airbag light.
I wouldn't touch an SLK with a 6 foot pole because of the high cost of upkeep and the poor fuel economy. Nothing personal, they are beautiful cars.

I just sold my 1995 E300D with 188k miles for $1500. It needed $3000 worth of repairs. The rear end was smashed and it needed the right rear quarter panel, the light, the trunk lid and hinges. The ABS is not functioning. It had numerous dents and flaws.

So, $5000 for a high mileage Mercedes diesel is not bad.
But for one blowing blue smoke, $3500.
The one with blue smoke will still run forever as long as you keep adding oil so it can continue blowing blue smoke.
Many areas don't check the emissions on these older Mercedes diesels, they are exempt.
When looking at these cars the things you have to look at are rust!
Motor mounts... does the engine shake alot?
Also, the brakes... these are heavy cars and a pep-boys break special will leave you with a car that doesn't brake like it should.
Being able to change a fuel filter (Sooo easy. 10 minutes $20 ) is a good idea.
A couple of other tips.
If the A/C doesn't work it could need a recharge or it could need the ( I forget the name, but its buried under the dash and cost $2500-$3000 to replace)
If the sunroof doesn't work... forget about it. Some mechanics refuse to repair them because they are such a pain.
All that being said. Buy one. Just don't buy a 240 with an automatic. SLooowww...
Do not buy a pre-1998 E320 with the 6 cylinder engine or any C-class with a 6 Cylinder. The head gaskets blow all the time.