SCOTTY, HERE IS WHY TOYOTA IS RUNNING 0W-8 VS 0W-16 ON THE SAME 2.5L HYBRID ENGINE!
It isn't a mechanical difference—it's EPA compliance vs. vehicle weight and duty cycle.
Here is the real breakdown of what each viscosity grade actually does inside the Dynamic Force 2.5L:

0W-8 (Ultra-Thin Economy):
• Primary Benefit: Maximum EPA fuel efficiency (squeezes 0.5%–1% better MPG on light sedans like the Camry).
• Realistic Lifespan: ~200,000–250,000 miles under normal commuting.
• Trade-off: Very low high-temperature shear resistance. Under heavy load or extreme heat, protection drops fast.

0W-16 (Balanced OEM Recommendation):
• Primary Benefit: Meets EPA fleet standards while offering slightly thicker film strength for heavier vehicles (RAV4/Highlander).
• Realistic Lifespan: ~300,000–400,000 miles on standard maintenance schedules.
• Trade-off: Better protection than 0W-8, but still thin under high thermal stress.

0W-20 (The Middle East & High-Temp Standard):
• Primary Benefit: Exceptional flow on cold starts while maintaining strong film protection under high thermal loads.
• Realistic Lifespan: Easily 500,000+ miles under severe service (taxi/uber/towing).
• Trade-off: Slight drop in EPA fuel economy numbers (~1% less MPG compared to 0W-8).

5W-30 (The High-Heat & Heavy Duty Protector):
• Primary Benefit: Maximum bearing and piston ring protection in hot climates (100°F+), heavy hauling, or severe stop-and-go driving.
• Realistic Lifespan: 600,000+ miles (1,000,000+ km) with regular 3,000–5,000 mile change intervals.
• Trade-off: Lose ~1–3% fuel efficiency, but virtually eliminates engine wear from oil thinning.

*(Assuming low RPM driving habits and strict adherence to maintenance schedules)*

-by Gemini

(i just wanted to cut ur stress Mr.scotty on the Oil confusion .. after seeing ur stress about it in this video:
https://www.youtube.com/watch?v=ajk-diaEpZY
hope this helps...)