What is everyones thoughts on using a high quality synthetic ATF like Amsoil,Redline,Mobil1 or Royal Purple ATF designed for Dex3 applications in place of DexVI.Just seems like a no brainer getting a full syn for a dollar or two more per quart than a mineral based fluid.I know the DexVI has a 6.0 viscosity and the others range in the high 6 to 7 range. Im not sure if this little change in viscosity could make a difference or not.
DexronVI vs Synthetic DexIII
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I think this is a very good question and have wondered the same myself.
I hope some of our resident transmission fluid experts like unDummy will take notice of this thread.
I hope some of our resident transmission fluid experts like unDummy will take notice of this thread.
I believe this has been answered before - but it's hard to find buried in one of the many Dex VI threads.
Dex VI is a VERY much improved GM Spec. GMN10060 is a solid specification and if you are really interested I recommend you get a copy and have a read. As mentioned it does have a lower 100°C viscosity. But it also controls the vis at cold temps and puts a 4.5 cSt@100 min requirement on the base oil blend. Combined with some decent performance requirements this limits the amount of viscosity enhancers. Which drives Dex VI blenders to use good base oils. The additive package can only be Afton HiTec at given treat rates.
All that said - this does not make a generic Dex VI better than a well made synthetic ATF for Dex III applications. Especially in high heat, stress and load applications. A good synthetic base oil and a robust additive package can easily exceed the test requirements of GMN10060 and meet all the cold temperature specifications.
If I had a 1971 454 Malibu or a 2004 Corvette or 1999 towing rig that called for Dexron, I would use a good proven synthetic Dexron III.
Dex VI is a VERY much improved GM Spec. GMN10060 is a solid specification and if you are really interested I recommend you get a copy and have a read. As mentioned it does have a lower 100°C viscosity. But it also controls the vis at cold temps and puts a 4.5 cSt@100 min requirement on the base oil blend. Combined with some decent performance requirements this limits the amount of viscosity enhancers. Which drives Dex VI blenders to use good base oils. The additive package can only be Afton HiTec at given treat rates.
All that said - this does not make a generic Dex VI better than a well made synthetic ATF for Dex III applications. Especially in high heat, stress and load applications. A good synthetic base oil and a robust additive package can easily exceed the test requirements of GMN10060 and meet all the cold temperature specifications.
If I had a 1971 454 Malibu or a 2004 Corvette or 1999 towing rig that called for Dexron, I would use a good proven synthetic Dexron III.
ok ,what is the best syn dexIII ? any test results by independant labs?
Thanks Pablo, that's good to know!
I'd also be interested in seeing any data comparing synthetic dexron III with dexron VI.
Lots of synthetic Dexron III's may be better than Dexron VI, or they may not. Without some data, there's no way to know. With Dexron VI, the spec is very specific, so you KNOW what you're getting.
Lots of synthetic Dexron III's may be better than Dexron VI, or they may not. Without some data, there's no way to know. With Dexron VI, the spec is very specific, so you KNOW what you're getting.
So, run some UOAs & get Terry to "read" the results b/c you're not going to get any test data comparing the two specifications. At least the UOA would be some data to go by.
Going to replace Mobil 1 synthetic Dexron II with Castrol Dexron VI in a few weeks. Have about 32,000 miles on current fill. I sort of expect to see no difference. When I went from conventional Dexron III to Mobil 1 I did see a bit of smoothness improvement.
That comparison does exist, at least in a very simple form. There is a graph in one of the GM SAE papers comparing some synthetic fluids with DEXRON-VI in oxidation. What it shows is that DEXRON-VI is at least as good and compared to some, much better.
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