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Old 12-07-2002, 06:51 PM
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Location: USA
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Why Put Transmission Fluid In Diesel Tank?

I have a 1991 350SDL with 147K miles(original owner).

I have heard that adding some transmission fluid to the fuel tank can be beneficial.

Is this true, what does it do, how much should I add, how often, what kind of transmission fluid should I use?

I have a intermittent rough idle.

Thank you.

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Old 12-07-2002, 07:57 PM
jcd jcd is offline
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Forget the tranny fluid, use Redline Diesel Fuel Catalyst

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Old 12-07-2002, 08:43 PM
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Location: OH
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A trucker had told em about tranny fluid !

A trucker has told me abt tranny fluid but I thought he was joshing me, perhaps not. What is supposed to be the effect of tranny fluid?
All the redline diesel products seem to do the same exact thing, except for the cetane additive?

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Old 12-07-2002, 08:57 PM
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Location: Canton,Texas
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Correct me if I'm wrong, but I believe that ATF can produce some unwanted ash that isn't good for rings/pistons..... it can be useful when trying to start a car that has been sitting (a little in each injector or glowplug hole and left sitting overnight to free the rings) but isn't good for regular use. The idea is that it provides lubrication and the detergents in it disolve deposits when added to the fuel. PowerService, Standyne, Redline or the Rotella fuel additive would be better though.
1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k
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Old 12-07-2002, 10:49 PM
The Least of These
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Although there are many reasons for rough idle, I believe a rough idle in your car may proceed engine failure. You may want to do a search. I hope I am wrong. Good luck.
1996 (W210) E300D 86K - Traded in for a Lexus
1992 (W124) 300D 2.5 Turbo 202K - Sold
1983 (W123) 300D, 146K - Sold
1970 280S, 263K - Sold - Beginning of addiction
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Old 12-08-2002, 01:37 AM
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tranny fluid is a cheap way to raise cetane a cpl of points but it does leave ash a better way would be to use some Two Stroke oil it will do the same thing and not leave ash.

Remember "If it ain't broke don't fix it"
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Old 12-08-2002, 02:09 AM
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Redline 85+, Power Service, or Shell Rotella additive, you can't go wrong with!
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Old 12-08-2002, 03:37 AM
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I went to a local CAT dealer and asked about Trans.fluid a couple years ago. I was told that 30 years ago when CAT recommened using tran.fluid when changing fuel filters, the fluid did not have as many additives as in it as today. My mechanic say's MB recommened using it then...but not now. Too much ash.
1983 300SD 343K everyday car
1983 300SD 285K from junk yard-tooks parts from deer car- runs great. Brothers car.
1984 300SD parts car-Hit deer
1979 300D 175K non-turbo "Doctor"
1979 300d parts car
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Old 12-08-2002, 10:28 AM
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I work at a Catterpillar dealer and I would be very carefull listening to "truck drivers". There are alot of very intelligent truckers out there but some of these drivers have a difficult time putting there pants on the right way!

Atf is added to the fuel tanks to prevent "waxxing" of fuel. Pariffin wax solidifies in the fuel at about -10 deg f. plugging the fuel filters. Our300sdl has a thermostaticly controled fuel heater and the fuel tank is in the car so I would'nt think you would need any fuel additives. Water in fuel is the most common problem with fuel filter pugging but most people think it is jelled fuel.

If you have a problem with your engine running rough it is a mechanical problem. Dumping in additives will only mask the problem. It is posible that you got some bad fuel but unlikely. Maybee you have a bad nozzle, low fuel pressure,low compression, plugged fuel filter or something wrong with an individual pump.
87' 300sdl
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Old 12-08-2002, 10:37 AM
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BJ300SDL is very kind to truck drivers. I think he should run for political office with that kind of diplomatic writing.

The earlier diesels were designed before the US bureacrats mandated low sulpher diesel fuel. Adding just a LITTLE oil to the tank would bring the lubricity up to the level necessary to prevent injection pump damage. The later models, however, have hardened barrels in the pump and require no additional lubricity in the fuel.

The truckers and others who are gullible enough to listen to old wives tales, believe that ATF is a cure all Penecillin for motor vehicles. As Wasuchi indicated, there are additives in ATF that are not healthy for the combustion process in your engine.

For those with injection pumps built before about 1987 or so that have not been updated with hardened barrels, just a few ounces of clean motor oil in the tank will add adequate lubricity without adding the nasty additives found in ATF. Most of the aftermarket additives do a good job of cleaning the system, but do little to raise the fuel lubricity.

Good luck,
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Old 12-08-2002, 11:40 AM
The Least of These
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Are you saying that it is only necessary to add fuel additive to prevent gelling in less than -10F?
1996 (W210) E300D 86K - Traded in for a Lexus
1992 (W124) 300D 2.5 Turbo 202K - Sold
1983 (W123) 300D, 146K - Sold
1970 280S, 263K - Sold - Beginning of addiction
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Old 12-08-2002, 12:05 PM
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Our300sdl has a thermostaticly controled fuel heater and the fuel tank is in the car
I had never heard of this, tell me more. Does my '86 SDL have this?
Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
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Old 12-08-2002, 05:24 PM
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The heater is above and behind the IP -- fuel from the lift pump it circulated through it when the temp is low. Can cause hard start problems if the o-rings go bad and let the fuel leak back into the tank.......

Of course, it won't help if the fuel in the filter is solid, though!


Intermittant rough idle on a 603 can be dirty injectors or bad engine mounts. If you cannot see the tapered portion of the mounts on the bottom, or if there is obviously oil leaking out, you need new ones. Very easy to replace if you have jack stands and a floor jack, or an engine hoist to lift the engine. One bolt top and bottom.

The notorious bent rod problem is evidenced by horrible engine clank (not injector noise) and excessive oil consumption, often occuring suddenly. Injector knock isn't a cause for alarm.

You may also have defective tappets, or bad o-rings on the center "bolt" on the oil filter housing cap -- if they are rock hard and leaking, the oil will leak down out of the tappet gallery and cause loud tapping noise and rough idle until the tappets re-fill. The o-rings are not in the oil filter package, you must get them separately.

1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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Old 12-08-2002, 10:00 PM
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There are several ways to approach fuel additives.

The smartest thing you can do is get your diesel from a truck stop because they go through thousands of gallons of fuel each week so your getting fresh fuel. And they already put the additives in the underground tank so you don't have to mess with it. If your not sure if it is blended fuel ask the attendant. The method that I prefer is to use a 50/50 mix of #1 and#2 diesel fuel. This is good for about -30 deg. f . If your running in arctic conditions you can run straight#1 or keroseen. I would not even consider using any additives or blended fuels unless it is -0 deg f. One advantage that additives have is that you won't loose any fuel ecconomy. When you use #1 or keroseen it has less BTU's that #2.

REMEMBER if your fuel gels you just can't add additive and it will melt gelled fuel it has to be added before it gels

I have only seen OTR trucks gel a couple of times in the past fifteen years. And remeber the fuel tanks on a truck are hanging in the breeze where most MB that i'm aware of are in the cabin out of the wind.

When I am at work tommorrow I will try to get exact temps. when fuel gels
87' 300sdl
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Old 12-09-2002, 12:49 AM
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The old wives tale use to have you run a quart of tranny fluid in your fuel tank. I did this in the 220D we had. Mercedes did a test back in the 80's about this and quite a few other additives. The conclusion was that the tranny fluid really did not help the injectors or injector pump. In fact it did cause some injector problems.
What Mercedes did conclude was that Chevron Techron is the only additive that Mercedes recomends for injector/pump cleanning. However do not add to much. It does thin the oil slightly if you add a bottle to every tank of fuel.

The second problem you may have with the diesel is gelling. The 220D manual has a mix chart to cut your diesel with gas to help prevent this and make the #2 diesel a #1 diesel. Those in the northern latitudes will find #1 diesel were we southerners only find #2. I have never had a gel problem in 22 years of owning a Diesel. I have usually had the car below the Mason-Dixon line.

The last diesel problem is algae. The only solvent I know for this, which is approved by Mercedes is Diesel Doctor.

I have stopped the tranny fluid in the tank, actually stopped that when I sold the 220D in 1990. The cars since the 220D I have only used Techron ( 240D, 2-300TDs, 300SDL and the E300). I also use the Techron in the 560SL.
I asked a Chevron fueler about the concentration of techtron in the premium gas. The dosage is 1/2 of the bottle mixing instructions. I do not know if they put it in the diesel, but I have never seen Chevron diesel.


1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car
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