I found this a while back and posted. Some good reading From a GM tech bulletin:
Although DEXRON-VI (fig. 1) was introduced into production starting with 2006 model year vehicles (see bulletin 04-07-30-037D), there are still some misunderstandings about it. Here are some facts to help clear up these misunderstandings.
Since GM introduced the first service-fill specification for automatic transmission fluid (ATF) in 1949, it has been necessary periodically to upgrade the specification as part of a continuous improvement strategy. The upgrading process ensures that available service fill fluids are of an appropriate quality for use in transmissions that have been designed around the improved factory fill fluid performance.
IMPORTANT: As with previous upgrades, DEXRON-VI fluids are designed to be backward compatible with earlier transmission hardware. But more important, earlier type fluids are NOT FORWARD COMPATIBLE with transmissions that were designed to use DEXRON-VI.
DEXRON-VI can be used in any proportion in past model vehicles equipped with an automatic transmission, in place of DEXRON-III (for instance, topping off the fluid in the event of a repair or fluid change). DEXRON-VI is also compatible with any former version of DEXRON for use in automatic transmissions.
TIP: Simply topping off the fluid is adequate, but a full drain and replacement is preferred, to obtain the full benefit.
IMPORTANT: DEXRON-VI Automatic Transmission Fluid (ATF) is the only approved fluid for warranty repairs for GM transmissions requiring DEXRON-III or prior DEXRON transmission fluids.
TIP: Any vehicle that previously used DEXRON-III for a manual transmission or transfer case should now use p/n 88861800 (88861801 in Canada) Manual Transmission and Transfer Case Fluid. And power steering systems should now use p/n 89020661 (89021183 in Canada) Power Steering Fluid.
TIP: Since some early bulletins were issued, further validation has taken place and certain transfer cases and manual transmissions now DO use DEXRON-VI, so it's important to refer to the owner manual for appropriate recommendations.
All licenses for DEXRON-III expired at the end of 2006 and will not be renewed. Fluids sold in the market after that date bearing claims such as "suitable for use in DEXRON-III applications" or similar wording should be avoided, because 'DEXRON-III' fluids are no longer checked and policed by GM and therefore may not be the originally tested and approved formulation.
ADVANTAGES OF DEXRON-VI
GM uses an ATF for factory fill that provides significantly improved performance in terms of friction durability, viscosity stability, aeration and foam control, and oxidation resistance. In addition, the fluid has the potential to enable improved fuel economy and extended drain intervals. The service fill specification for a fluid meeting these standards is designated as DEXRON-VI.
When compared with earlier automatic transmission fluids, DEXRON-VI offers these improvements and benefits:
- enhanced performance of both new and older transmissions
- longer ATF life (160,000 km/100,000 miles normal, or 80,000 km/50,000 miles severe). It is important to refer to the owner manual because certain vehicles recommend a normal service drain interval of 150,000 miles (240,000 km).
- consistent shift quality throughout the life of the transmission
- extended transmission life.
To achieve these benefits, DEXRON-VI offers significant improvements in these operating characteristics:
Friction Stability (improved 100%) -- Friction describes how the fluid behaves when transmission clutches or bands are engaged. A fluid with poor friction characteristics leads to grabbing, chattering and slipping (fig. 2).
DEXRON-VI also offers a 120% improvement in clutch durability (fig. 3).
A DEXRON-III
B DEXRON-VI
A Clutch operated with DEXRON-III
B Clutch operated with DEXRON-VI
Viscosity Stability (greatly improved) -- Viscosity is a description of how thick or thin a fluid is at various temperatures. In a hydraulic system, components can function sluggishly or improperly when viscosity is wrong. As determined by comparison testing (fig. 4),
DEXRON-VI maintains an almost constant viscosity over time, while the viscosity of DEXRON-III degrades considerably.
A DEXRON-III
B DEXRON-VI
Foaming Resistance (improved 150%) -- Automatic transmission fluid may contain air in three forms -- dissolved, entrained (aeration) and foam. Oil containing air doesn't do anything very well -- lubrication is affected, heat transfer in affected and pressures are unstable. Anti-foam additives are used to control and limit the effects of air in the fluid (fig. 5).
A DEXRON-III foam test
B DEXRON-VI foam test
Oxidation Resistance (improved 100%) -- Oxidation describes the length of time it takes for a fluid to reach the end of its useful life. Oxidation generally occurs more quickly at higher temperatures (fig. 6).
And oxidation has an effect on how long a fluid can be used before replacement is necessary.
A Aftermarket fluid oxidation test
B DEXRON-VI oxidation test
TIP: Just because another auto maker does not require use of DEXRON-VI, this does not imply that their required fluid is in any way inferior to or better than DEXRON-VI. It simply means that the other auto maker has established its own, unique fluid requirements. Their transmissions may be built with different materials, and may be designed to perform in different ways, neither of which is necessarily inferior to or better than GM's transmissions, just different. Variables include the material used for friction surfaces, the material used for reaction surfaces, the types of control mechanisms and the characteristics of the factory fill fluid. This means that each manufacturer must tailor their transmission fluid requirements to meet the needs of their own transmissions. And a fluid may cause entirely different performance when installed into transmissions of different designs.
COUNTERFEIT PRODUCTS
Beware products that claim to be DEXRON-VI but are not; for instance, some products claim to be multi-purpose. And beware the products which claim to provide DEXRON-VI characteristics when added to other ATFs. Unlicensed products have not been tested by GM to determine whether they meet GM's specifications.
ADDITIVES
DEXRON-VI is formulated to meet and exceed GM's specifications and requirements. Additives are not needed and are not recommended.
The best thing that can happen when using an additive is that it will do nothing. At worst, an additive can ruin the transmission.
DEALING WITH CONTAMINATION
Anything but DEXRON-VI in the automatic transmission is considered a contaminant. Typically, a customer or other service facility may add fluids other than DEXRON-VI. This includes aftermarket additives -- they are not needed and should not be used. In case like this:
- drain the transmission fluid
- flush the system with DEXRON-VI (NOT solvent)
- fill the system with the correct amount of DEXRON-VI.
FLUSHING
Many aftermarket flushing systems rely on solvents, which essentially may be considered contaminants. The effects of these contaminants may lead to transmission failure.
Refer to bulletin 02-07-30-052E and also document 1601517 for the complete story on using the Automatic Transmission Oil Cooler Flush And Flow Test Essential Tool J 45096 TransFlow. Here are some highlights.
Two significant features of the J 45096 are (1) that it uses DEXRON-VI, not solvent, as a flushing agent, and (2) that it injects high pressure air into the fluid stream to agitate the ATF oil to enhance removal of contaminated ATF and debris.
TIP: It is important to flush the system in both directions (back-flush and forward-flush). There are instructions in SI to explain how to make the proper hookups for both directions.
There are also instructions in SI explaining which adapters to use for various transmissions.
TIP: It is necessary to fabricate adapters for Vibe, Wave and Aveo, using instructions in SI. Also, although these vehicles have a slightly different transmission oil requirement, the small amount of DEXRON-VI remaining in the system after flushing is compatible.
In addition to the flushing capability, the J 45096 also has a digital flow meter to check and indicate the flow capability of the ATF oil cooling system.
Oil temperature has a direct bearing on flow rate, so SI explains several ways to ensure that the DEXRON-VI in the storage reservoir is suitably warm for an accurate test. And there is a table showing the minimum flow rate at various temperatures and for both steel and aluminum coolers.
