Older Mercedes Diesels...

Such as these...
http://bringatrailer.com/2010/12/12/bat-exclusive-clean-1985-mercedes-benz-300td/

Why do they get such poor mileage? No turbo?

Lots of factors. Heavy. Old-technology torque-converter automatic transmission. The engine is indirect-injection, which is not as efficient. Aerodynamics are not the equal of newer vehicles.

Heavy body. So-so aerodynamics. Heavy engine. Non-locking torque converter.

1985s are turbo, and have taller gearing / better economy. It was also the last year for the W123.

-J

The heavy body is one of the biggest killers, these things are tanks! My friends dad had one and we would pull their old huge boat with it. That thing was a beast... But is dad spend tons of time working on it...

The Diesels do get much better economy than the gas models though. A 280 would struggle to crack 18 on the highway and would probably do about 12 around town with the AC on... on premium

-J

What's poor economy? My W124 2.5L has averaged 32 MPG since I bought it. Drive it hard locally it'll get 29, take it on a trip and drive it gently it'll get 36. This is a 3,600 car with a non-lock-up torque converter 4-speed. Turns 3000 RPM at 75.

Not bad for a 20 year old car that is quieter and rides better than the current Passat, and has an engine that legitimately go over 500,000 miles.

I think it is all relative. My W126 300SD, with the big all-iron 3.0L 5 cylinder got the 2-ton car to mid to high 20s through its non-locking 4sp slushbox. That is literally about TWICE what the gas version could. Granted the gas version would run circles around it (and probably has a good 40+ MPH top speed advantage).

Even my 7700 pound 7.3L F350 can hit 19 unloaded, also a 4sp slushbox and a 4.10:1 rear end to boot! 19 sounds bad, but I assure the 7.5L gasser couldn't get much past 10, and loaded down it would be around 5 whereas my diesel is maybe down to about 14 MPGs at the worst and doesn't care how much weight you have hanging off the back.

I talked to a guy with an F250 Powerstroke at a filling station once and he told me the truck gets 17 MPG empty, loaded, and towing 6,000 lbs. Doesn't care. The M-B doesn't care that much either. And ironically (at least when you look at what a box the car is) the W124 had the lowest drag coefficient of any sedan sold in the world in the late 80s, .28. So it may take a while to get to 80 MPH, but it holds it effortlessly once there.

My old 300D would get around 30mpg. Not bad considering all the things everyone mentioned. Also, those cars are geared low. MB has them geared low so you're always have some power at hand for acceleration.

MB mindset back in the day was economy meant a car that could last 500,000 miles, not high MPG. The engines are underboosted for longevity. Only two ways to kill a MB turbo: neglect your oil, the turbo oil feed pipe cracks.

I miss my 300D, but not enough to buy another one.

My 82 240d 4spd manual averages 28 mpg and has seen 32+.
Granted it is slow and heavy but also solid, dependable and very cushy compared to my Jettas

IndigoBlueWagon said:

I talked to a guy with an F250 Powerstroke at a filling station once and he told me the truck gets 17 MPG empty, loaded, and towing 6,000 lbs. Doesn't care. The M-B doesn't care that much either. And ironically (at least when you look at what a box the car is) the W124 had the lowest drag coefficient of any sedan sold in the world in the late 80s, .28. So it may take a while to get to 80 MPH, but it holds it effortlessly once there.

Click to expand...

My 2011 F350 (6.7 Powerstroke) tow truck would do the same.

14Mpg in each direction on a 100 mile tow, with a Lexus on the back of it.

I had a car like this for about 4 years (in the 90 th). Bought it with 361K miles and sold it at 600,000 miles. Drove every day over 300 miles and many times more... Miss that car a lot, but I'm retired now and don't need 3 cars or more in the driveway. Mileage was ok and it is a Turbo Diesel(TD). For the time being great.