Fuel mileage and diesel Benzs... - Page 3 - PeachParts Mercedes-Benz Forum

JimSmith · #31 04-23-2002, 11:16 PM

Guys,

The cars themselves improved drastically as well. The drag coefficient of a W123 is probably more than 20% higher than a W124 or a W201, and even higher compared to a W210.

Since the great majority of the engine's output at highway speeds is being used to punch a hole in the air for the car to run through, it should not come a surprise that older, less aerodynamically efficient shapes need more power than newer, more efficient ones. In addition, most cars have begun to use more aluminum and other lighter weight materials that also help lower fuel consumption.

Hope this helps explain the lower mileage of the W123 machines compared to the newer models. Jim

GregS · #32 04-23-2002, 11:31 PM

As for the transmissions, I believe all 300 and 240Ds came with a 4speed automatic. I'm not sure if the 4th gear is an overdrive, but I can tell you it sure doesn't SEEM like and overdrive because the motor really screams on the highway. My car turns around 3400rpm at 72mph, and its pretty loud.

On the other hand, if I were looking for a w123 like you are, I would definitly go with an '85, because people on this page say that the '85s come with a lower rear axle ratio.

Lastly, I use Power Service additive simply because I am concerned about keeping the pump lubricated well. I read a lot about the fact that the sulphur content of diesel fuel was lowered around '92, and that contributed to accelerated wear in injection pumps. I am not an expert on the subject, but I figure an additive with a lubricant can't hurt. Also, I used to live in upstate NY, and an additive was required in the winter or else the fuel would gel when temps dropped to around 10 degrees.

Greg
'84 300D

#33 04-24-2002, 02:09 AM

I concur with Diselhead. 24-26 consistently. I have tried 65 mph and 75-80mph, just don't think it changes much. Took a trip to Las Vegas and drove 576 miles non stop, put in 19.5 gallons, Mobile Diesel, 29.53 mpg. This was ALL highway mileage, no traffic, no stop and go!

Good Luck.

Jim Stevens

1985 300DT

ohcaptainron · #34 04-24-2002, 01:23 PM

I have owned a nine mercedes diesels, all purchased new, with better than factory maintence, synthetic oil, mobil one, last five years mobil delvac one. no additives, BK44 every six months.
1980 240D 26 city 33 highway
1982 300D 25 city 29.0 highway
1983 300D 24.7 city 28.4 highway
1984 300sd 24 city 28 highway
1985 300 D-TD 24.5 city 29.4 highway still own it 198000 miles
1987 300D 24 city 27 highway
1990 300SD 23 city 25 highway
1993 300D 29 city 35.5 highway
1999 E300D 27 city 33.8 highway Current car has been chipped 215HP
I travel to Germany on a regular basis and long for a E320 CDI
A few notes: I drive high altitude mountain roads, Consumption can vary 20% in the winter because of the lower BTU content in the winterized fuels. Hope this helps. I think you can safley say If you buy a Benz diesel 25 MPG is average.

#35 04-24-2002, 02:11 PM

I'll add one other weird thing about mileage:

Commuting, I often drive 90% of the time in 3rd gear, both on my 240D manny tranny and my 300CD auto tranny. That doesn't seem to have any significant effect mileage. A tank-fill after 100% of commuting miles shows about the same mileage as a tank-fill after 100% highway miles. I don't understand how this can be, but I've observed it often.

The Warden · #36 04-24-2002, 03:11 PM

Quote:

Originally posted by GregS
As for the transmissions, I believe all 300 and 240Ds came with a 4speed automatic. I'm not sure if the 4th gear is an overdrive, but I can tell you it sure doesn't SEEM like and overdrive because the motor really screams on the highway. My car turns around 3400rpm at 72mph, and its pretty loud.

3400 RPM's at 72?!? WOW that's high...my truck turns less than that at 75 mph (it's pushing it's 3300RPM redline), and the rear end gears are 4.10's with no overdrive...

I just have to ask, but are you sure it's going into high gear? Or is that a normal RPM operating range for a W123?

And I have heard of 300D's coming with a 3sp auto...not sure on the accuract on that, though. And mais oui the 240D's were also available with a 4sp manual tranny.

25mpg's acceptable for me

although I may see what I can do about increasing it some after getting a car...maybe try to find a 5sp OD manual and try to shove it in

{added on edit} I actually made a post earlier, I think on this thread, about the difference between summer fuel and winter fuel...but I don't see it now; I guess it disappeared into cyber space?!? Or it was on a different thread...

DieselHead · #37 04-24-2002, 04:25 PM

These engines do rev high but I think they sound best at higher engine speeds. They're a little bit loud (compared to modern gassers) but the engine has a certain silkiness that really makes you feel good about your car. Also, eventhough it's loud, it really doesn't sound like it's working too hard.

Alex

andy · #38 04-24-2002, 05:56 PM

A few questions. 1. How much fuel does a 300d/cd Turbo/non-turbo hold? 2. How much fuel is left when the fuel light comes on? How exactly is everyone coming up with their MPG? (# of miles from fill up divided by gallons used from fill up to fill up?) The fuel light used to come on at about 450 miles from each fill up. I don't remember how many gallons of fuel was used, but I think I came up with 27.5 MPG. After a few tank fulls of bio-diesel it comes on at about 400 or so. I have changed both fuel filters twice since my first tank of bio-diesel. What I might do is filler up and just drive until I run out(having a container of fuel in trunk) to see how many miles from full to empty. I will also be able to see how many miles I can go after the fuel light comes on. andy

GregS · #39 04-24-2002, 07:15 PM

In responce to the question whether my tranny is going into 4th gear - yes it is. My tranny shifts perfectly, and 3,400rpm is what it always turns when I'm cruising on the highway. I admit, my speedometer is not accurate, but I guess that since I keep up with traffic on the highway, I must be going between 70 and 75mph.

Greg
'84 300D

rickjordan · #40 04-24-2002, 07:58 PM

For figuring MPG, just use the trip odometer. Divide the number by the # of gallons the tank takes. Just reset the odometer at every fillup. Recently I went 292 miles on 10 gals, =29 mpg. BTW the TDs only have 18.3 gals tanks, even still that's a cruising range of about 500 miles on one tank. I have one question though regarding the "reserve", where is it. I mean as Bill put it for the D/CDs the tank has a reserve of 2.8 gals. Is that just when the low fuel light comes on?

Capt Kirk · #41 04-24-2002, 08:49 PM

4th gear is 1:1

MB had 3 speed Auto's but those were on the V8's (450SL, 450SEL 6.9, etc)

As far as my mpg goes, I get 2.5-3 weeks on one tank of gas. I drive about 200 miles a week (at least thats what my other car says, the 300D's odometer is dead)

deezuhl · #42 04-24-2002, 10:32 PM

On my dads 85 300D Turbo he generally gets 22mpg his best was 26mpg. On my 87 300D Turbo I average 25mpg my best was 30mpg. On my brothers 87 190D Turbo he averages 30 mpg his best I believe was 35mpg

The Warden · #43 04-25-2002, 04:01 AM

Quote:

Originally posted by TXBill
Warden, I have never heard of a 300D with a 3 speed. You must have read that on mb-diesel-cars.com Lots of misinformation on there. I know there's one guy that keeps insisting that the only difference between a turbo and a non-turbo engine is the turbocharger. I stopped trying to correct them.

Yes, that 3400 rpm is right. The Mercedes engines are designed to rev high, unlike most American engines. The redline on a MB diesel is close to or higher than 5000 rpm. My SD has no redline marked on the tach actually.

Bill, how'd you guess? I actually started out there when searching for information (and looking for a BBS similar to Ford-Diesel.com, a place I go to for my two beasts that has been unbelievably helpful), and was disappointed by the apparent lack of participants...fortunately one of the guys there mentioned this site and I've been here bugging you guys ever since!

I'm real happy with this site; when I found this place I've stopped looking...and now this is one of the 3 places I try to go to daily. I've pretty much stopped going over to mb-diesel-cars.com...

And I'm suprised that that RPM's is considered normal; OTOH, I'm so used to the low-revving American diesels that I almost forgot you could make a diesel capable of going over 4K RPM's without breaking anything. Not complaining, but it's something I'll need to get used to...and interesting that M-B decided not to use an overdrive gear, but if they feel that 3400RPM's is the optimum speed for the engine, I'm okay with that.

*crossing fingers hoping the van sells quickly*

rickjordan · #44 04-25-2002, 08:22 AM

Yeah, the TD's tank are smaller mostl likely due to their location, underneath. Still as I mentioned a travel range of about 500 miles is nothing to sneeze at. Hell, I could drive from one coast to the other and only fill up 6 times.

Gary F. · #45 04-25-2002, 12:27 PM

I have a 85 300D. It has aprox. 185,000 miles. I use Pennzoil 15w40, Quaker State Dextron III in auto trans. I consistently get 24 to 26 mpg, mostly highway driving. I rarely exceed 3000rpm, I am a light foot driver.