Diesel W123 MPG. Lets get real! Chime in with your MPG - PeachParts Mercedes-Benz Forum

ChrisArnt · #1 11-29-2013, 12:10 PM

OK. So we see these on Craigs and on Ebay with people claiming outrageous MPG.
I know the VW diesels can actually get 50MPG.
But, I've had half a dozen of these.
My 81' W123. I usually got around 24. The best I ever got on an all highway trip with over inflated tires I got 33MPG.
On my 95 W124the best I ever got was 37MPG on an all highway trip on a very cold night, other than that mid 20s.
I'm looking at a W123 Diesel wagon with a 4 spd. He claims 40-45 MPG.
I know that love can make a man do and say things that aren't quite true.

What MPG do you get?
Do you do anything special to get it? (Eco mods, synth oil/ trans fluid, air dams, smooth caps etc..)

tjts1 · #2 11-29-2013, 12:35 PM

Quote:

Originally Posted by ChrisArnt

On my 95 W124 I once got 37MPG on an all highway trip on a very cold night, other than that mid 20s.

Thats pretty good for an automatic. The problem with these threads is everyone posts their one time best tank under ideal conditions. The long term average over multiple tanks (which most people don't calculate) is far more important.

uberwasser · #3 11-29-2013, 12:36 PM

W123 300D, OM617.912, automatic - 25mpg average mixed city/highway on B99. Would be a bit higher on D2.

Phil_F_NM · #4 11-29-2013, 12:44 PM

Last January when I drove across the country in my 1978 300D, I got above 32mpg on the freeway. My best mileage was after a fill-up at Capitol Oil in Topeka. I made it all the way to eastern Ohio. There I made the mistake of getting diesel from a mom and pop filling station and I think it was either gelled or had water or algae in it. My fuel economy went down the toilet after that.

Once I changed my injectors to newly reman'd Bosch units from Pelican, my daily commuting fuel economy went up. Before the injector swap it was low 20's in the city. Afterwards, it was mid-high 20's depending upon traffic. There were a few places there in Hudson and Bergen counties that I had to drop the car in low and floor it to merge onto route 1-9. Daily driving around there I'd get about 26-28mpg average but I had to dilligently watch my tire pressure and ensure that I go good fuel from one of the truck stops which had a high volume.

Phil Forrest

whunter · #5 11-29-2013, 12:53 PM

1976 300D automatic transmission (no turbo)!!!

This car is totally Stock.
Up to 70 MPH, my daughter gets a solid 21 city - 25 highway MPG, even when treating it like a sports car.

Above 70 MPH the MPG seems to fall, roughly 1.65 MPG per 5 MPH.

Example: MPG 18 when driving 90 MPH, and the engine is NOT happy.

.

zorecati · #6 11-29-2013, 01:09 PM

I don't have a 123 but my 87 w124 has never gotten less than 30mpg with a best of 34. The 30mpg was a tank full of 85 to 90mph drives though my 70mile one way commute. The 34 was doing 55 to 65mph depending on speed limit.

I recently started to record the mileage.

https://www.fuelly.com/driver/zorecati/300d?fu=5523902

tjts1 · #7 11-29-2013, 01:21 PM

Quote:

Originally Posted by zorecati

The 34 was doing 55 to 65mph depending on speed limit.

I recently started to record the mileage.

https://www.fuelly.com/driver/zorecati/300d?fu=5523902

One of these days I should really try driving that slowly for a whole tank, I've heard great things about it. Unfortunately 55-65 around here relegates you to the slow lane where the pavement is full of potholes from heavy truck traffic. Those same trucks will also be tailgating and passing you on the left.

+1 on Fuelly. Surprisingly few 300d drivers are using it. Its an excellent tool to track mileage, cost per mile and I also use it for oil change intervals.
Mercedes-Benz 300D MPG Reports | Fuelly

mach4 · #8 11-29-2013, 01:28 PM

Here's my mileage on a recent coast-to-coast trip in October (San Diego to North Carolina) This is my 107 with a 617.952 engine, 722.3x transmission and 2.47 rear end. The 107 has about a 200# weight advantage, but with luggage and 2 passengers, some of that was likely countered.

Note that my odometer reads 10% high so the mileage numbers are raw while all the other numbers have the correction factor built in.

Wind, altitude, braking, speed all have a huge impact on mileage.
The 2.47 rear end probably helps a lot- 2600 turns at 70mph. My "normal" everyday around town is usually around 29.

WNC123 · #9 11-29-2013, 02:25 PM

Quote:

Originally Posted by ChrisArnt

I'm looking at a W123 Diesel wagon with a 4 spd. He claims 40-45 MPG.

Would you please ask him to join the forum and post his methods as to how he gets this fuel mileage? I would love to get 40-45mpg in my '85 wagon. Heck, I'd be happy to get 30-35mpg.

It's been a while since I thought it was necessary to calculate my fuel economy. When I did I was averaging 23-24mpg all around, city and highway combined.
Now I just look at it like this: when I am putting fuel in my tank, I multiply the # of gallons by 22 and that's how far I figure I can go on that particular fill up (almost never fill all the way up, usually put in $20-$30 for around town puttering). Then again, I seldom pay much attention to the (trip) odometer and almost never reset it when I put fuel in.

greazzer · #10 11-29-2013, 02:52 PM

My old DD was a 1985 300D Turbo, and was mostly stock. It achieved 25 MPG +/- 2 MPG consistently, and that was running either #2, WVO, or a blend. It did not matter.

My current DD is a 1983 240D with a 300D NA (non-turbo) and 5 speed Getrag 717.400, but it has a higher ratio diff. After some recalculations of my initial testing, it achieved 27 MPG consistently before mods. With mods, e.g., power steering delete, et cet, it achieves 30 -31 MPG on #2, WVO, or a blend. It does not matter. I am thinking a 2:88 will help out a little also since most of my driving is highway miles.

I know a gallon of WVO has less BTUs than a gallon of #2, but I have not seen any difference. Even a blend with RUG, I really do not see a difference and RUG has the least amount of BTUs than WVO or #2.

Once I get the car back from the paint guy, and re-install the water injection and complete deleting the mechancial water pump and vacuum pump, et cet., I will test the MPGs. My overall goal is 35 MPG, however not sure that is ultimately doable unless I shed some weight. Off my gut as well. LOL.

I would say that the folks who are hitting 40+ MPG are either mistaken, misleading, or they drive extremely frugal. There are contests where folks compete in regular cars and they hit some incredibly high numbers. However, those driving habits would be tough to keep on a daily basis, e.g., always drifting downhill, turning off the car while drifting, driving no more than 55 MPH, et cet.

A VW hit 80+ MPG New world record: 1,626 miles on one tank of gas - CSMonitor.com

rocky raccoon · #11 11-29-2013, 04:13 PM

Car is 1983 300CD. Fresh oil change with 15W-40 AMSOIL. Fresh valve adjustment. Fresh air filter and fuel filters.

Starting miles: 290788. Ending miles: 293341
Total miles driven this trip: 2553

Trip route:
Leg 1: Near Richmond VA to Tampa, FL via U.S. 1 to U.S. 301 (no interstate hwys)

Leg 2: Tampa to Ft. Lauderdale. No interstate hwys
Car parked in Ft. Lauderdale for 5 days.

Leg 3: Ft Lauderdale to Charleston, SC. No interstate.

Leg 4: Charleston SC. to Home. Interstates all the way at speed limit (65 to 70 mph).

Air conditioning most of the way, cruise control used where feasible. Ran speed limit. Did not avoid small towns.

Fueled 10 times (kept at 1/2 full).

Threw out the high mileage and the low mileage and averaging the rest provided a real world mileage of 29.456.

Skippy · #12 11-29-2013, 04:45 PM

'83 300D, stock except for a four speed swap from a '77 240D, tires aired up to 36-40, and driven hard enough that I wore out my last set of tires in 17,000 miles. My last fill up came out to a bit over 26 mpg. I typically get 24-25, but can hit 30 on long highway trips.

Delibes · #13 11-29-2013, 05:35 PM

My 1982 300TD wagon got a consistent 24-25MPG with mixed driving (60% HWY, 40% CTY), and topped at 31MPG on a trip from VA to RI, driving between 55 and 65 MPH. The 1987 300TD wagon was 80% HWY, 65-70MPH, and returned between 28 and 30MPG.

Zacharias · #14 11-29-2013, 05:56 PM

Quote:

Originally Posted by ChrisArnt

I'm looking at a W123 Diesel wagon with a 4 spd. He claims 40-45 MPG.
I know that love can make a man do and say things that aren't quite true.

I emphatically disagree. Curbsiding makes vendors do and say things that aren't true.

If the car isn't too far away, and taking the time to go see it doesn't take precious minutes away from such vital functions as, say, nosehair trimming or teaching the dog to vacuum, by all means go.

If it involves major time and/or travel... don't say you weren't warned if you get there and a lot of other claims are fanciful too, like it has a floor, never seen salt, idles like a Honda, blah, blah blah.

Stupid claims in ads aren't part of the game. They are asshat alerts.

ROLLGUY · #15 11-29-2013, 06:21 PM

Quote:

Originally Posted by Delibes

My 1982 300TD wagon got a consistent 24-25MPG with mixed driving (60% HWY, 40% CTY), and topped at 31MPG on a trip from VA to RI, driving between 55 and 65 MPH. The 1987 300TD wagon was 80% HWY, 65-70MPH, and returned between 28 and 30MPG.

Miguel, it is nice to hear from you again (even though you are stuck in Spain). Now back to our regularly scheduled topic- Of all the 123's I have checked, (617 turbo/automatic) the average is around 24-27. I get around 30ish with the 240. This is all with WVO/RUG blend, so D2 may give higher numbers.