AARON, Do you believe that synthetic motor oil promotes leaks on new engines?

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98 E430(sport), 99 ML 320 (sold) , 05 C 230(sport) Mark

I didn't switch to synthetic engine/tranny oils until my car had 185,000+ miles. I was also told by another mechanic that leaks may ensue, and at 285,000 miles still no leaks. I've never been told to not change the fluids, no matter the color or miles, just doesn't seem to be common sense.

I think I've read somewhere, "change it hot, change it often." Can't go wrong with that advice.

Brian W.
92 400E
90 300E
87 260E

First, as regards ATF vs synthetic, I think that some mechanics become confused about the detergent properties of synthetics in general, and tend to assume that leaks have developed from the detergents wearing away build-up that has formed around gaskets. There should be no harm from changing to a synthetic.

I was doing some research on the use (by some people) of ATF as a fuel additive in both gas & diesel engines. During that process, I spoke to several transmission shops and even a refiner of ATF.

One of the things that came up was what is being discussed now on this thread. Their explanation of the issue was this, if the transmission has been SEVERELY neglected, and not serviced, your fluid will be dark brownish and smell like burnt toast. Once it has been neglected to that certain point, varnish and worn transmission particles will have glazed themselves to the interior parts of the transmission, and it's just a matter of time before the transmission will need to be rebuilt.

Now, it would seem logical that one would immediately want to change that fluid and filter, but from what the experts say, the detergent properties of the old fluid in there is long since worn out. Changing the fluid replaces the old worn out non-detergent fluid with fresh active detergent laden ATF. The ATF will now act as a solvent, wash away the "glaze" and make it a swirling abrasive fluid that will both circulte the harmful deposits, and remove whatever grip was left on the bands from the "glaze", quickly resulting in slippage.

Either way, the trans is headed for the shop, but in this extreme example, changing fluid will actually shorten the length of time until it gets rebuilt/replaced. However, due to the new formulation, Dexron III, transmission shops are seeing less and less of this happening, and a lot of it was older cars that used Type-F. Also be aware that there are additives in ATF that when exposed to rubber, cause the rubber to initially swell, and later disolve into a jelly-like substance...

[Edited by longston on 03-14-2001 at 07:02 PM]

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Scott Longston
Northern California Wine Country...
"Turbos whistle, grapes wine..."

I had my tranny on my 81 sd back flushed an it shifts better.a definite no no on atf in the differential ,but you do use it in the manual tranny in the old 74 240 d sure surprised me when I first got the car and drained it for a refill ,as I had no manual at the time I called the dealer here in Eugene Or and they told me to use atf in the manual. By the way the people at the Eugene Or. M.B. dealership are the politest I have ever dealt with . The last time I called them the head tech man stopped what he was doing and came to the phone to answer my question.
William Rogers.....

How does it work on the newer Mercedes, you do not need to change the transmission fluid at all? I just don't get it? That goes against all logic and common sense that us humans have learned to know. Anyone know??

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

How interesting. So if it's possible that the fluid could last 300K miles on a new Mercedes, why would it not be possible to have the ATF last 300K miles on my 1995 C280? What is the difference, albeit the ATF tester and dealer hookup, sensor, etc. Theoretically, wouldn't it be possible that mine could do the same as a newer Mercedes? How would the transmission itself affect the fluid life? Blackmercedes, you're full of info!!

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

Volkswagen has the same idea with their new auto trannies, sealed for life! There is no way to check the fluid short of a computer, therefore no transmission shop can flush the system (and there are no external fitings inorder to flush the system). The owners manual specifies that the atf is good for the life of the car, not to be changed. I asked about changing at the dealer and the reply was "why would you wnat to spend $250 on oil?" (they use synthetic fluid aswell). They have no way of draining the torque converter either, meaning a change only removes 2-3 quarts (8 quart capacity). Silly what the auto makers are doing.
As far not changing the atf, this advice was founded on domestic cars, which apparently need new trnasmissions every three years anyways!!!!
Changing the fluid once it is already burnt is risky, but failure is going to happen anyways at that point, the mechanic just doesn't want the heat when it fails to frive away from the shop. Mercedes transmissions are strong and should have regular changes, I change my fluid every 50000 miles (less then two years), and at 525000 miles it still shifts and runs fine!