I don't trust trip computers. They're accurate in some situations and totally inaccurate in others. Without documenting miles traveled and fuel pumped into the tank at every fill up, the data is useless especially when making claims far outside the well documented norm.
I kept track of every fill since the day I bought this car with an automatic transmission. With the automatic it averaged
29.8mpg over 7,900 miles and then after the 5 spd swap it averaged 38.1mpg over 14,500 miles. Theres a 27.8% difference between the manual and automatic transmission.

The S124 wagon suffered a huge weight and aerodynamic penalty vs the sedan which has been well documented. Your numbers sound about average for an automatic wagon.

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CENSORED due to not family friendly words

And comfortable/.......

It's scary fast, as contrasted with the then new 220D and 240Ds / autotrans my folks bought, that I was weaned on as a teenager.

The foreign country 2.7 liter versions of the I6 CDI sold overseas are likely plenty fast enough, and perhaps more fuel efficient than our 3.2 liter U.S. lightening quick and fast version.

Other than their cost, I have no idea why anyone would choose an old W123 diesel instead of the W211 CDI as their DD? They win, and win big in every category.

Well, since you seemed determined to snark about my claim on this and at least one other thread, I stopped on my way home from work to fill up, even though I still had another week or so before needing to...

Total on the odometer for the last TWO fillups was 1261 miles. The car had 30 or so miles on it when I started the trip. The total round trip was 497 miles each way, door to door.

Whilst we were in SC, we used the car for 168 miles of around town driving. My buddy was driving and we frequently left the car idling with the A/C on when our spouses jumped out to do some quick shopping. This, of course will reflect on the total average, necessarily dropping it down. He has a fairly heavy foot as well.


Total gallons for the trip was 30.82. Computed mileage is 40.91 mpg.
I did fill up at my usual station, a Hess, near my home both just before the trip and today. Car was level, facing the same way, and topped off in the usual manner.

The trip computer read 42.1 for the 1261 mile average.
I've also mapped the odometer of the car to the Garmin mileage, and find it is also close enough to consider it to be accurate.

There you go.



Now perhaps we should cast the same harsh light on your claims for your 300D.

At one time I owned both a 1986 5 speed manual W124 M103 300E and a 1987 automatic W124 300E. Both sedans. I could consistently over the years I owned them get 22-23mpg out of the automatic, and 24 -25 out of the 5 speeder. That's about a 10% difference in favor of the manual.

Your claim of a 27% improvement is almost 3X the difference I had with two FACTORY spec cars. That seems like a pretty big difference..... Care to explain.

Regards,

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

Friday, the day before I flew out to pick up the CDI from Tyler, I drove my 95 E300 diesel to work. I thought I was still driving a modern car.

After 1500 miles driving back in the CDI, I got into the 95 E300 diesel on Monday and was amazed at how vintage it felt......

Not that I do not appreciate and enjoy the two W124 cars I have....

But... I've put 14k miles on the CDI since I bought in October last year, and hardly drive the cabriolet anymore on a daily basis. It's now a pleasure car....

Like Skid Row Joe says, if you have not driven/owned one of these cars, you have no idea what they are, and what they are capable of.

Jim

__________________
14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

TJTS1 has moved this discussion over to another post.

See this thread for my last post on this matter.

shocked a guy with true 240 fuel economy

Jim

__________________
14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

I've been tracking my fuel economy for a couple years ago on Fuelly.com. My results mirror others who post their results on the 05 and 06 CDI's here in the states. I've heard claims of mid to upper 40's but haven't acheived that personally. I've got 146K on mine now.

My fuel mileage has been slowly trending downwards over the last year and a half or so, and my 0-60 times are slower than they should be. Also, my trip computer seems to be around 2 mpg optimistic over my pen and paper calculations consistently. The highest fuel economy I've personally witnessed is around 43 MPG from a consistent 68MPH trip over a few hundred miles. I'm currently trying to diagnose my relatively low fuel economy -normally 32 in town, and I'm getting around 27MPG now. Highway fuel economy is also lower by a few MPG too. The Fuelly trend is showing it too.

Here are some things I've done in the process to help my fuel economy:

1)Replaced thermostat shortly after I purchased the vehicle.
2)Replaced Fuel filter.
3)Flushed/replaced rear differential oil with appropriate spec oil
4)12-14 Qt flush of tranny with pan drop and filter change
5)Injector leak off test performed. Results appear SAT
6)Verified boost pressures reported to computer are correct by comparing them to an analog calibrated boost gauge.


I'll be stopping by a Mercedes INDY today for alignment/suspension inspection so I will see if they can diagnose the car.

__________________
Josh


2005 E320 CDI

2002 VW Jetta TDI

I noticed that the thermostat made a big diference in mileage.

It appears this engine is very sensitive to temp, that is the engine doesn't fully lean out until the temp is at operating, which seems to be slightly above the 1/2 mark on the gage.

It's possible that the engine management is getting a bad signal and enrichening the injection shot more than it needs. If you are familiar with the old mechanical injection pumps, you can throw all that info away.... The CDI uses a system that is more like a modern EFI gas injection in principle, there are multiple shots of fuel for each combustion cycle, vice just a single pulse from the mechanical style. An across the board performance decrease suggests that you are not at optimum fuel delivery for the cycle.

Why? Hard to guess with the given info. These are complex cars, but they have an ability to tell you things with the proper equipment. Have the mechanic hook up an SDS system and see if he can diagnose the problem.
If your mechanic doesn't have the interface, find a mechanic who does.


Jim

__________________
14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

Thanks for the additional information regards the thermostat, Jim. My CDI does run very cool for quite a time on the coolant temperature gauge. When the DC fans run, it's only for a brief time I've noticed. I haven't driven the car but a couple thousand miles in the 13 months I've owned it. (2,700 mi) most very short rips like two to five miles from home on errands.

Joe, Under those conditions it would not be unusual for me to see a cumulative rating around 30.

When my wife uses the car for errands, it's under these same severe conditions, stop and go, low speed, short runs, etc., and I note a significant lowering of the average mpg on the trip computer.

When you can drive a CDI in the following manner:

1. Constant speed.
2. Significant duration.
3. Fairly flat terrain.
4. Drive as Jackie Stewart recommends.
5. Car is in peak tune.

You can indeed get way, way above the EPA range.

Absent one or more of the above, and you will not achieve peak efficiency. It's not normal for me to get all 5 going for me at once. But, boy, when I do, it's pretty impressive.

Jim

__________________
14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

Joe,

That is pretty severe service in my opinion as well, because you may not be getting the engine oil up to temperature. You may have water building up in your oil pan. Water + dissolved contaminants can produce acid, which will eat the bearings and the cylinder walls and other things. That damage will take many years to cause engine failure, but it will eventually.

A new thermostat may allow the engine to get up to operating temperature more quickly, but I'd recommend that at least once or twice a month, you drive for 30 minutes or so in order to drive the accumulated water out of the engine oil (and the transmission oil, power steering fluid, differential...). You may want to consider changing your engine oil annually, despite the low mileage, or at least send in a few samples for lab analysis to see what's going on.

My '95 E300 takes about 10 minutes of driving before the engine coolant temperature is normal. My '87 300TD only takes about 5 minutes of driving. My understanding is that the engine and transmission oils don't reach operating temperature until about 15 minutes of additional driving after the coolant reaches normal temperature.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Here's some interesting MPG data on the 2006 E320 CDI on Fuelly.com

From a low of 21 to high of 34 average MPG, none even close to 46 MPG.

2006 Mercedes-Benz E320 Mileage

Anyone else use fuelly,com? I joined recently to track my 3 diesels 85 300D, 92 VW Eco diesel and 81 VW diesel pickup and have data on my 92 Eco only- 3 fill ups so far, avg 45.1 MPG

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Who on this list has EVER claimed to have an aggregate long term MPG average of 46 MPG from a MB CDI?

It sure wasn't me.

See post #39 for the the confluence of conditions that were required to obtain the single trip high reading.


Jim

__________________
14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

No one! I posted it for those who thinks they may see 46 MPG and be disappointed they will never see 46 after buying one. I can see your 46 MPG was higher than actual when you fueled up at a higher tank temperature than when you started driving. After a long drive, the hot fuel in the tank would have expanded requiring less fuel to fill up than if the tank was at the same temperature as when you started.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

double

Want to see 44-46 MPG from a CDI? I'm almost 100% sure anyone can if they drive it a constant 50MPH on a flat road with no headwinds on a nice day with the tires inflated to 40PSI and the A/C off. I'm also betting you could get 38 MPG out of an OM603/W124 combo under the same conditions.

Nobody here ever stated you could get 46MPG on a daily basis under normal driving circumstances. The data you reported from fuelly sounds about right for someone that is driving primarily in a suburban environment - and its what I'd expect to get if I was driving in such an environment.

The expanding hot diesel thing is certainly a real issue, however that is only an issue if your re-filling from a tank that is fairly full - if you're checking mileage after the reserve light has come on and you've got 1.5 gallons of 'hot' fuel in a 21.5 gallon tank I don't see it as a significant factor.

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98 Dodge-Cummins pickup (123k)
13 GLK250 (135k)
06 E320CDI (323K)
16 C300 (62K)
82 300GD Gelaendewagen (54K)

Have you had the car scanned with an Mercedes SDS machine? If so were there any latent codes? Was the rail pressure up-to-spec?

Power and fuel economy loss together would seem to indicate a timing issue but that's all under control of the computer - have you checked exhaust system backpressure? My CDI seems to have some sort of CAT in the exhaust system and I've know a few gas powered MB's to suffer symptoms like your seeing after a cat partially failed and caused high exhaust system backpressure. This would effect power and mileage at the same time.

__________________
98 Dodge-Cummins pickup (123k)
13 GLK250 (135k)
06 E320CDI (323K)
16 C300 (62K)
82 300GD Gelaendewagen (54K)