Apparently, Subaru has recommended a special, lightweight 75W80 gear oil for manual transmissions that have "beat the syncro" shifting problems. The part number is K0323F0091.
My basic understanding of gear oils is that putting a 75W80 in place of the usual 75W90 or 80W90 may provide better syncro action and faster shifting, but at the expense of gear protection under heavy loads or shocks.
Can you experts weigh-in with opinions on this? Seems odd that Subaru would recommend a lighter oil for their heavily stressed manual transmissions.
My basic understanding of gear oils is that putting a 75W80 in place of the usual 75W90 or 80W90 may provide better syncro action and faster shifting, but at the expense of gear protection under heavy loads or shocks.
Can you experts weigh-in with opinions on this? Seems odd that Subaru would recommend a lighter oil for their heavily stressed manual transmissions.