You might have the alignment checked. It can get so out that it actually slows the car down a bit like having a dragging brake, yet still not be noticable by the driver. I just recently had mine fixed and it had scrubbed both front tires down to almost bald on their inside edge before I noticed.

I don't know how much it will affect my mileage since the issue was only recently resolved, but the car does seem to coast a bit better than it used to.

__________________
'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

Update: Good news!

Thanks for all of the suggestions. I am now getting what Mercedes originally estimated for mixed/town driving ~20mpg. On the last two tanks I have gotten 20.6mpg and 19.6mpg. Here is a list of what I did:
- changed the primary fuel filter
- changed the secondary filter (don't forget to order the o-rings)
- installed a K&N air filter
- changed the flexible brake lines (one was leaking and may have let the pads hang)

Still need to check the valve adjustment (just got the wrenches)...

I would get rid of the K&N. It will lead to a dusted engine. The factory filter is more than adequate for the power level of this engine.

When you adjust the valves, while you have the valve cover off, you can do a rough check of the timing chain stretch. Let us know if you need directions on how to do that.

I'd recommend (if your state allows) blocking off the EGR, both vacuum line and the exhaust side - use a steel plate. If your EGR fails open it can rob a lot of power and increase fuel consumption. It also contributes to a really dirty intake manifold.

I personally think that K&N filters will simply allow more dirt into the engine and wear it out faster (turbo ensures that the engine is getting all the air it needs) so I'd restore the stock set-up and just use a good quality filter like Mann, Hengst, or Mahle.

__________________
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

Over 15k miles still getting the 20mpg until last tank. Had a glow plug failure last week and while I was there I replaced all of the weeping injrctor return lines. Also put in a new inline filter. Only one tank and only highway but got 27mpg! Need to run a couple of more tanks to make sure it wasn't a measurement error.

Is it possible the return lines were leaking that much?

Yes & if they are you are well on your way to a failed motor mount on that side!!

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

Very good call. Had to replace the motor mount(s) when I first got the car. Now I understand...


@Maxbumpo,
Thanks for your help with my fuel consumption troubleshooting. Would you please point me to the posting that explains timing chain stretch measurement?
Thanks.

Please put your car in your avatar or sig.

Signature test

__________________
1985 300D (W123 Turbo Diesel)

Thank you, this allows folks to know your car with any post. You're doing better than me, I recently changed my sig, now it doesn't appear.

The FSM file is too large for the site, e-mail me.

I agree.

There is NFW that a 617 turbo gets 20 mpg unless the mileage is 100% stop and go in the city.

For reference, the SD is getting a certified 28.5 in mixed driving (85% highway) using winter fuel!! I'm positively impressed.

Last year, I was suffering with figures about 23.5 due to a slipping ODO. $150. later...........that's history.

The SD does have a 2.88 and 215-65-15's and it also has a designed highway speed of 62 mph (designed by me )

Drip Timing Threads
Drip Timing Threads

Need Automotive Grade Prozac = timing chain

HELP! I need to check stretch!

Diesel Timing Chain Thread

Diesel Injection Pump Timing Device threads
Diesel Injection Pump Timing Device threads

IP Full Load Adjustment 617 Turbo
http://www.peachparts.com/shopforum/diesel-discussion/214412-ip-full-load-adjustment-617-turbo-post1772106.html

Specialized Indicator for IP Timing
Specialized Indicator for IP Timing

IP Timing
IP Timing

Setting timing with IP lock tool.... Why won't the plunger set?
Setting timing with IP lock tool.... Why won't the plunger set?

IP Destroying Injectors, GP, and Prechamber?
IP Destroying Injectors, GP, and Prechamber? [long]

wont start for anything!
wont start for anything! 1985 300SD


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__________________
ASE Master Mechanic
https://whunter.carrd.co/

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
2003 Volvo V70

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