In the US, manufacturer's recommendations are intended to optimize engine life versus CAFE. They will recommend the lowest possible viscosity in order to reduce internal friction losses, raising fuel economy by hundreths of a mile per gallon. You'll never notice the fuel savings on an individual level, but it helps the manufacturers the fleet level.
You're worried about your car, they're worried about their continued ability to sell SUVs with their own zip codes to suburban soccer moms.
Whatever the manufacturer recommends, I typically go up one grade to get into the comfort zone and away from the edge of the cliff.