Are older transmission fluids different from today's fluids?

toyota
camry

#1

I have some 7-8 year old Dexron III (Mercon), both from Castrol and Proline, that I would like to use along with freshly bought Dexron VI. Does transmission fluid degrade over time or is it not a good idea to mix manuf or grades of Dexron in my 90 Camry?


#2

The DEXRON III does not degrade in the bottle. The DEXRON VI is compatible with the DEXRON III. You can add the DEXRON VI to a system with DEXRON III but do not add DEXRON III to a system specifying DEXRON VI.

If you are doing a transmission fluid change, you can use the old DEXRON III and add some DEXRON VI, it might even provide a benefit, but if it does provide a benefit, then it will provide even more of this benefit if you use all DEXRON VI.