Originally Posted by Timothy Barth

I am about to change the auto trans fluid in a 2005 c6. The owners manual calls for DexronIII. Is this fluid still available or can I use DexronVI ?

Originally Posted by RicK T

Use the VI.

Here is the GM announcement of the VI and it states right at the beginning that it is backward compatible with prior trans:

(the thread is titled wrong, saying dexron 4, it is actually 6)

https://www.corvetteforum.com/forums...exron-4-a.html

Originally Posted by timd38

GM did it to reduce SKUs, if you look at the viscosity difference between the two, you would want Dev III.

Originally Posted by Timothy Barth

What are SKU's?

Originally Posted by Timothy Barth

I am about to change the auto trans fluid in a 2005 c6. The owners manual calls for DexronIII. Is this fluid still available or can I use DexronVI ?

Originally Posted by GOLD72

I assume your car is an auto transmission?? If yes, Dexron 6 can certainly be used though the original spec was for Dexron III. If it is a 6-speed manual stick, absolutely do not use Dexron 6 as it is too thin for manuals. There are plenty of aftermarket fluids that meet Dexron III specs that are acceptable for the Tremec manual trannies.

Originally Posted by cclive

100% If it is an auto trans then Dex VI is fine, but if it is a manual, you should absolutely not use Dex VI...use Dex III only. There are many ATF fluids out there that meet Dex III specs but not Dex VI specs...these are the ones to use. I used Mobil One Synthetic ATF, which specifically says that it meets Dex III but not Dex VI. Dex VI has a lower friction coefficient which does not work well with the synchros in a manual trans. It was made to increase gas mileage in automatic transmissions. Mine is a 2007, and Dex VI had been out on the market for years at that point, but mine has a sticker right next to the fill plug that says use Dex III only...they did this for a reason.

Originally Posted by glass slipper

It was not done to reduce SKUs, GM had to come up with a new fluid/SKU for manual transmissions that used Dexron III before. GM stated Dexron VI is backward compatible with Dexron III first and foremost because it is and secondly because GM stopped monitoring the Dexron III specification after Dexron VI came out meaning any Dexron III transmission fluid you buy today states it meets the Dexron III specs, it does not say it has been approved to the Dexron III specs because GM doesn't even monitor the spec now. If you buy fluid stating it meets the Dexron III specs from a good company like Amsoil or Mobil, you'll be OK.

While there is a difference in viscosity between the Dexron VI and Dexron III when new, the big change when GM went to the Dexron VI is stable viscosity over the life of the fluid. Dexron III actually shears down in viscosity and quickly becomes "thinner" than Dexron VI. There were many other improvements made to Dexron VI vs Dexron III, it's really a no brainer to make the move to Dexron VI when changing automatic transmission fluid in cars originally calling for Dexron III. Dexron VI is a substantial upgrade over Dexron III plus Dexron VI enjoys the added benefit of GM monitoring the spec while you're pretty much on your own with Dexron III.

Originally Posted by Timothy Barth

Mine is an 4sp automatic. If you drop the pan and replace the filter, how much fluid will you have to replace?

Originally Posted by cclive

I don't have a service manual for '05 so I can't tell you how many quarts...but my rule is to buy more than needed and then return the unopened bottles. Someone will chime in with the right amount of fluid.

Originally Posted by jft69z

For a 2005 the GM eSI says - Overhaul: 10.8 qts & for Pan removal: 5.0 qts.