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Fuel filter change interval

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bobaran's picture
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I am looking for recommendations for fuel filter (main and pre-filter) change intervals. I last changed both about 14 months ago. That was approximately 12,000 miles. I am also interested whether running Biodiesel (B20) would increase/decrease the time between fuel filter changes.

I appreciate any advice.

Thanks,
Bob

1992 300D 2.5L Turbo 162,800 miles

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Maxbumpo's picture
Mount Pleasant, SC
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1987 300TDT
Re: Fuel filter change interval

Main filter and pre-filter are scheduled to be changed at 30k mile interval.

However, whenevery you experience a rough running engine and any power loss, first thing to do is change both fuel filters, regardless of how old. The main filter is also a water separator, but it only holds a small amount of water. In the winter time, this water can freeze in the main filter and cause a no-start or poor running condition, and if you have lots of water in the fuel tank it will begin to 'spill over' from the main fuel filter, be consumed by engine causing rough running, and if you don't correct it that water will cause damage in the injection pump and in the injectors.

If you see build-up in the pre-filter, your tank may have a microbial 'bloom' in you tank, which occurs when bacteria and/or fungi live in accumulated water and eat the diesel fuel. Promptly treat with a biocide (available at boating stores and marinas) and also de-watering additive, be prepared to change the pre-filter once or twice while cleaning out the bloom.

Here is a Chevron website with a nice diesel fuel technical review that will tell you all you need to know and more about modern diesel fuel:
http://www.chevron.com/products/prodserv/fuels/diesel/

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Max Dillon
Charleston SC
'87 300TD, 334k miles (need to pull the head again...)
'95 E300 Diesel, 335k miles (daily driving duty)
'73 Balboa 20

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BobK's picture
Williamstown, KY
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1988 560SEL
1986 300SDL
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1976 300D
Re: Fuel filter change interval

Not sure what the factory recommendation would be for your car. I like to change them at least ever 1000 gallons of fuel. Biodiesel can clean out some of the baddies that show up in the fuel system so yo may need to change them a bit early if this is the first round with the biodiesel. I try to buy the clear prefilters so I can see how clogged it is getting. If it looks bad, ya change it. I have had main filters so bad that the car was loosing power on newly purchased cars. Over all, filters are pretty cheap yet quite important so I don't see much downside to doing them fairly often. One old diesel I bought had an opaque white prefilter that seemed to be restricting fuel. I replaced it and cut it open. It was half full of sediment!

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rogo's picture
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Re: Fuel filter change interval

You could always use the Maintenance Schedule in the W124 Mercedes Service Library CD. 60,000 miles is the interval for your 1992 300D 2.5L Turbo.

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95 E300D

nhdoc (not verified)
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nhdoc's picture
Re: Fuel filter change interval

The filters are cheap and easily replaced. Water is more of a concern than clogging to me as I have experienced first hand what happens when the main filter gets waterlogged. So basically I change mine once a year, in the late fall regardless of how many miles I have driven but usually that works out to 10-15K. I know that is more frequent than doing it by the book, which I think is 30K, but like I said, it is very cheap insurance.

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Re: Fuel filter change interval

Thanks for all the learned responses. I have been using the clear pre-filters. The first time I tried biodiesel, the pre-filter immediately turned an opaque orange. I changed both filters and that has not happened since, regardless of the fuel type.

I concur that changing the fuel filters is cheap and a wise thing to do. I am frankly amazed by my Mercedes. I purchased it with 149,500 miles. It now has 163,000 miles. I exclusively use synthetic oil and have not lost even a half-quart of oil between any of my oil changes.

I have a question for Robert or other members, where do I purchase the W124 Mercedes Service Library CD?

Thanks,
Bob

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Maxbumpo's picture
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Re: Fuel filter change interval

Bob,

Here is the list of most frequently requested info that I regularly share; see link at bottom for ordering the service manual:

MB motor oil recommendations:
http://www.whnet.com/4x4/oil.html

Star Tuned article on coolant:
https://www.mbwholesaleparts.com/StarTuned/pdfs/AntiFreeDec04.pdf

StarTek, On-line access to service manuals, EPC:
http://www.startekinfo.com/StarTek/index.jsp

Potomac German Auto used parts:
http://www.mbpartsonline.com/index.html

Rusty's MB parts wholesale:
http://buymbparts.com/

Vehicle data cards from Russian MB site:
http://www.mbclub.ru/mb/vin/?lng=eng

MBUSA Service Manuals:
http://www.classictechlit.mbusa.com/MB/

There are a couple things to understand about the MB service manuals.
(1) They are written for MB technicians who have already been through formal classroom training; many general mechanics knowledge-type procedures are NOT covered (for instance, MB techs are trained to perform a basic inspection of every car they work on BEFORE they work on the problem at hand: they inspect all tires, brake system and general axle health, to insure that the most important safety items are in place). In other words, this is not a step-by-step guide clearly explaining in full detail every item to take into account. Consider them more of a good checklist with pictures, to 'refresh the memory' for performing repairs that were already taught in the classroom once and then supervised while performing an apprenticeship.

(2) They are translated from German, and sometimes information is mis-translated or lost. Sometimes reading and understanding a procedure requires several read-throughs followed up by questions here.

(3) They are usually on CD (scanned copies of the book), and the navigation screens are not friendly, some computers have a hard time with the links, and the pictures can be very inferior. Also, sometimes really obscure procedures are left off the CD entirely. If you can find paper copies on Ebay, get them. Steve Nirvig has created a 'web page' front end index for the CDs, which you save to your hard drive and then access via Internet Explorer or Firefox; it makes the CD's much easier to use.

All that said, they are still the best resource out there. Consider also getting the "Technical Data Book for Passenger Cars" that covers your model (extensive technical data including torque values for all repairs), and if there is an "Introduction to Service" book for your car, get that as well (good primer of all the 'new' systems on the car to quickly bring technicians up to speed when a new model is introduced).

Lastly, join the Mercedes-Benz Club of America, which provides this website, for $45 per year. Your membership benefits include: Discounts on parts at dealership and some private resellers (Performance Products), six issues of 'The Star' magazine with great articles about the marque including technical highlights and Q&A, and local events (social as well as technical and autocross and rallye).

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Max Dillon
Charleston SC
'87 300TD, 334k miles (need to pull the head again...)
'95 E300 Diesel, 335k miles (daily driving duty)
'73 Balboa 20

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uberwgn's picture
Medfield, MA
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Re: Fuel filter change interval

Max, nice summary!

Bob, my game plan is to change fuel filter + pre-filter annually. I aim to do it either late fall or early winter to ensure I've rid the system of water that may be parked in the base of the spin-on filter. As other note, these components are cheap.

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