This car-care article appeared in my newspaper on October 28, 2003
Drive It Forever
By Bob Sikorsky
An article in Automotive Engineering magazine, the official publication
of the Society of Automotive Engineers, brought to light a great deal of
valuable information about automatic transmission fluids (ATF). ATF is
probably the most complex of all auto- motive lubricants, including even
the most sophisticated synthetic motor oils.
They can be made from as many as 15 elements. A typical motor oil may
contain seven. According to Automotive Engineering's article,
transmission fluids are subjected to severe oxidizing conditions that
* Deposits of sludge and vanish in the transmission;
An increase in corrosion of copper-alloy bearings;
* Hardening of various elastomeric, or rubber-like, seals;
Glazing, flaking and wear of clutch plates and bands.
Any one of these conditions ls bad news for your transmission and
wallet, but all can be avoided by changing to a high-quality
transmission fluid before oxidation can alter its protective
characteristics. The big question is how to know when that time has
A good rule of thumb is to follow the change interval given in your
owner's manual. For most transmissions in most areas of the country this
will do just fine. If you want to be more precise, just use the
time-proved paper towel test.
Here's what to do. Place a drop or two of transmission fluid from your
car -- you can get the drops by removing the transmission dipstick -- on
a clean piece of paper towel.
Next to this drop, place another one or two drops of equal size of fresh
unused transmission fluid. Wait one hour, then observe the spots.
The fresh fluid spot is your reference point. It will be large and have
a reddish or light-brown color. Compare your transmission fluid's spot
to the one made by the fresh fluid. Is it about as large as the fresh
fluid spot, and does it have some red or light-brown coloration? Or is
it a small dark spot?
Automatic transmission fluid that does not exhibit good spreadability
and coloration is probably suffering from oxidation and should be
replaced. A spot 'that approximates the color and size of the fresh
fluid indicates that the fluid is still fine and should be left in the
This test is easy to perform. It should be done about every two months
As soon as you notice the fluid getting darker and the spot getting
smaller and more concentrated, you will know it is nearing time to get
the old stuff out and the fresh stuff in.
One of the toughest decisions a car owner can make is whether or not to
change the fluids for the first time after a number of miles have
accumulated. At first this doesn't seem to be a problem -- fluids should
be changed periodically.
While that is true and the rules applies to all fluids in the car --
power steering, brake, coolant, oil, rear axle, transmission -- there
are times when an owner is caught in a Catch 22.
Here's a typical scenario. A car owner who has never changed the
automatic transmission fluid decides that he should take better care of
his present buggy. So, he thinks, I'm going to do it a favor and start
by changing the transmission fluid because that would be the most
expensive unit to replace. .
He does, but to his dismay, in a few days he finds the car dripping
transmission fluid from both front and rear seals. The car had never
leaked with the old fluid, why should it leak now? Isn't fresh fluid
supposed to be good for the transmission?
It's leaking because the owner's neglect allowed crud to build up inside
the transmission causing the viscosity of the fluid to thicken and
become a "false" seal. The crud locked in the old fluid and kept it from
leaking past the seals, which in the interim had become damaged.
When fresh fluid was added to the transmission, the new additives
attacked the false seals and opened a path through the bad seals so the
fluid could escape. Result? A leaking transmission. New seals and/or
gaskets will solve the problem.
To change or not to change, that is the question. Is an owner better off
with old fluid and a nonleaking unit or with fresh fluid and a leaking
unit? Talk about tough decisions, but the answer depends on how long you
intend to keep the car.
If you plan to keep the vehicle, you're better off with fresh fluid. New
seals or gaskets, if required, are an extra cost, but not as expensive
as a new car.
If you're going to get rid of the car, why ask for trouble?
To add to the confusion, sometimes when fresh fluid is added to a
high-mileage vehicle for the first time, it might not cause the unit to
leak. That could be the case with your car, but there is no guarantee.
If you decide to change any fluid for the first ' time in a car that has
more than 70,000 miles on it -- there is really no way to set an exact
number of miles -- you are, in essence, rolling the dice.
Bob Sikorsky, is a national-award-winning journalist who has written
several best-selling books on automotive care.
Questions or comments of general interest should be addressed to Bob
Sikorsky, care of this newspaper. Bob Sikorsky regrets that he cannot
answer questions individually.