Switching to Synthetic ATF with high mile trans
 

I've got a 1994 C220 with 120K miles and would like to switch to Mobil-1 Synthetic ATF Fluid. It seems the benefits outweigh the price tag. I am currently running Castrol Dexron III ATF Fluid. One reason for the switch over is that I can't stand the 2-3 upshift delay when the C220 is cold, but I suspect synthetic ATF won't help this.

A good friend of mine, a BMW mechanic, does not recommend switching over the Synthetic ATF with high mileage transmission (More than 60K) because he claims (at least with BMWs) that he has seen a lot of failures happen after the switch over. He believes that the detergents with the Synthetic ATF do too good of a job - loosening crud that eventually causes a failure.

Any thoughts on switching over on a car with 120K miles?

Also, when I drained/refilled the transmission (no torque converter)...I was only able to get 2.5 quarts of Castrol ATF into the transmission - I think it's underfilled, but the dip stick says otherwise. If I switch over how many quarts will I need (esp. after I drain the torque converter).

Thanks,
Chandra Bajpai
1994 C220 (another one with a bad wiring harness!)

Chandra:

Changing tranny fluids to synthetic, or changing it after not chaning it for a long time can sometimes "clean" the tranny too well, causing shifting problems and eventual failure. If the fluid has been changed properly, I'd not worry too much.

If you don't have an immediate problem, the tranny will last longer with the Mobil 1, possibley significantly longer (as in 100,000 miles longer or more). Much better lubricant.

The one thing I would do is change the filter shortly after switching -- if a lot of crud does flush out, it will end up in the filter.

An MB tranny will only take about 2.5 qt without draining the torque conveter -- most of the fluid is in there, which is why draining is recommended. Certainly, if you do switch to Mobil 1, you need to drain the converter.

The 2-3 delay cold isn't the tranny, it's the computer, and there isn't a thing you can do about it. It's there to warm up the catalytic converter or something like that, but since the computer controls the shifting, you cannot change it.

Peter