So Im going to flush the tranny and change the oil, car is garage kept hanst been driven or changed since july of last year so I was wondering the best oil for it and tranny fluid, its the 3800 v6 3.8l.

 

If the tranny is stock, you can't go wrong by using DEXTRON III. If it is modified, you will have to experiment.

 

Well a lot of fluids meet dexron III requirements. I personally like Royal Pruple's ATF or TCI blue racing fluid. I recomend Royal Purple for High HP motors!

 

I have heard that Royal purple oil SUPPOSEDLY increases HP in the LS1 engine is, it true for the 3.8 liter series II engine ?

 

DEXRON VI has just been released by GM and it is a much improved auto trans fluid. It can be used anywhere DEXRON III was used.

 

Cool, thanks for the tip.

Some details are here:

Dexron VI

 

Dexron VI is a little expensive right now.

 

Maybe so, but seems more than worth it... Strangely a local GM shop I am using did not even have Dexron-VI, and had to special order -- bulk ATF was still Dexron III... They seemed to be largely unaware of it, despite being out for 1 yr+ Same is true for Murray's -- they hadn't heard of it, and cannot special order it -- yet.

Automatic Transmission Fluid — DEXRON® VI
The most recent release of the DEXRON series of automotive transmission fluids. It features the same low temperature performance characteristics as DEXRON IIE.

Size:
1 qt.
1 gal.
55 gal.
Item #:
88861003
88861045
88861046

Summary:
Petro-Canada ATF Dexron-VI Approved from General Motors
The First Approval from General Motors for all 2006 & beyond (Check out Downloads)

Applications:
Petro-Canada Dexron®-VI ATF is recommended for all 2006 and beyond GM vehicles with Hydramatic automatic transmissions. It is fully back serviceable for Dexron®-III (H), III and IIE applications. Meets GM specification, GMN10060. Always consult your vehicle owner's manual for specific recommendations.

Petro-Canada was granted the first DEXRON®-VI ATF license number from General Motors (J-60001).

FEATURES & BENEFITS:
Extended fluid life

Extends life of transmission
Potential to extend drain intervals
Enhanced Product Performance for newere and older transmissions

Outstanding resistance against sludge & deposit formation
Improved oxidation and thermal stability versus Dexron®-III (H) ATF
Superior anti-wear protection
Outstanding low temperature fluidity
Enhanced foam control which maintains responsive shifts and reduces wear on bearings, bushings, and gears
Improved Fuel Economy versus DEXRON®-III (H) ATF

Improved torque transfer versus DEXRON®-III (H) ATF
More consistent viscosity profile which maintains a consistent torque performance
Lower viscosity versus DEXRON®-III (H)
Improved shear stability
This unique fluid is specially formulated to provide twice the service life of a DEXRON®-III (H) ATF and offers enhanced performance for both new and older transmissions.

Straight from GM:
General Motors DEXRON®-VI Global Service-Fill Specification

More details from the 1st Dexron-VI licensee:
Petro-Canada TechData DEXRON®-VI ATF Automatic Transmission Fluid