|Newer doesn't always mean better
Question : MY 1993 Toyota Corolla 1.6SEG has clocked 240,000km. The automatic
transmission fluid (ATF) has been changed regularly in accordance with
the owner's manual, which specifies a Dexron III ATF.
Toyota markets a Type-IV fluid but my mechanic recommends using either a
generic Dexron Ill or Toyota Type-III ATF. Which should I use?
THE typical characteristics of an ATF include its ability to flow at low temperatures, resistance to excessive heat and
oxidation, provide clutch plate friction at
different speeds, anti foaming properties
and the prevention of corrosion and deterioration of seals, gaskets and metallic
The biggest difference between the various grades of ATF is the amount of friction
it offers. Gearshifts must occur at precisely
the correct moment without delay or slippage, and in order to do so, the clutch
plates must automatically engage and disengage properly.
The proper engagement and disengagement of these clutch packs very much
depends on the level of friction between the clutch plates.
The ATF determines the amount of friction between the clutch plates and hence,
the shifting characteristic of your gearbox.
If the level of friction is too low, the plates
will slip and engagement will be delayed.
Conversely, if there is too much friction,
the shift will be too harsh or sudden.
Your mechanic is correct in advising you
to use Type-III fluid in your vehicle.