# Are older transmission fluids different from today's fluids?

**URL:** <https://community.cartalk.com/t/are-older-transmission-fluids-different-from-todays-fluids/63313>\
**Category:** Maintenance/Repairs\
**Tags:** toyota, camry\
**Created:** [April 3, 2011, 7:37pm UTC](https://community.cartalk.com/t/are-older-transmission-fluids-different-from-todays-fluids/63313 "2011-04-03T19:37:04Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jaanni](https://avatars.discourse-cdn.com/v4/letter/j/c67d28/32.png) [@jaanni](https://community.cartalk.com/u/jaanni)\
**Post date:** [April 3, 2011, 7:37pm UTC](https://community.cartalk.com/t/are-older-transmission-fluids-different-from-todays-fluids/63313/1 "2011-04-03T19:37:04Z")

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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?

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**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\
**Post date:** [April 4, 2011, 11:54pm UTC](https://community.cartalk.com/t/are-older-transmission-fluids-different-from-todays-fluids/63313/2 "2011-04-04T23:54:14Z")

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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.