"Genuine" stock parts, are, well, stock. There are always improvements that can be made over stock parts, which is why we see so many millions of motorists modifying their cars for better performance, handling, braking, etc. If you want top of the line, you want AMSOIL.
The AMSOIL Signature Series Synthetic Automatic Transmission fluid outperforms other fluids and at the prices I can get you, costs less to boot -
http://www.amsoil.com/shop/find/product/atf?zo=349698
AMSOIL formulated the worlds first 100% synthetic ATF way back in the late 1970's and has more experience with synthetic ATF's than any other company in the world.
Las Vegas Taxi Cab Field Study (G3118) (1.5MB PDF)
A Las Vegas taxi’s transmission and engine revealed virtually no harmful sludge or wear after 100,000 miles of severe service.
Protects Against Thermal Breakdown
Signature Series Synthetic ATF is formulated with high concentrations of antioxidants, making it naturally heat resistant. As a result, it provides outstanding protection against sludge and varnish deposits that clog narrow oil passages and contribute to clutch glazing. After 100,000 miles in severe service, fluid analysis revealed Signature Series Multi-Vehicle Synthetic ATF contained 41 percent of its original oxidation inhibitors, proving its long-lasting resistance to thermal breakdown.
Outstanding Wear Protection
Varying speeds and loads causes torque multiplication and extreme stress on gears and bearings. AMSOIL formulated Signature Series Synthetic ATF with high film strength and premium anti-wear/extreme-pressure additives to help prevent wear during severe service. In the industry-standard FZG Gear Wear Test, Signature Series Multi-Vehicle Synthetic ATF that had been used for 100,000 severe-service miles achieved a “Pass” at stage 12 – the highest stage. The results exceeded the Ford MERCON V and Chrysler ATF+4 specifications for new fluid, demonstrating the lubricant's long-lasting wear protection.
Cold-Temperature Fluidity
Cold, thick automatic transmission fluid lengthens shift times and reduces fuel economy. Signature Series Synthetic ATF is wax-free and delivers extraordinary cold-flow properties (< -60°F pour point). It helps improve shift response, energy efficiency and warm-up times.
Friction Durability
Today’s transmissions are smaller and must withstand higher horsepower and torque while delivering smoother shifts, all with longer fluid life recommendations. AMSOIL Signature Series Synthetic ATF is formulated with friction modifier additives that deliver outstanding clutch-holding capacity (static friction), torque-transfer ability (dynamic friction) and anti-shudder properties (slipping torque-converter clutches). Analysis reveals that after 100,000 miles in severe service, Signature Series Multi-Vehicle Synthetic ATF provides nearly identical friction properties as new fluid for smooth, reliable shifts.